Patent Publication Number: US-2023162974-A1

Title: Enhanced Perovskite Materials for Photovoltaic Devices

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 16/665,831 filed Oct. 28, 2019, entitled “Enhanced Perovskite Materials for Photovoltaic Devices”, which claims priority to U.S. Provisional Patent Application No. 62/770,313 filed Nov. 21, 2018, entitled “Enhanced Perovskite Materials for Photovoltaic Devices”, the entire contents of which are hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     Use of photovoltaics (PVs) to generate electrical power from solar energy or radiation may provide many benefits, including, for example, a power source, low or zero emissions, power production independent of the power grid, durable physical structures (no moving parts), stable and reliable systems, modular construction, relatively quick installation, safe manufacture and use, and good public opinion and acceptance of use. 
     PVs may incorporate layers of perovskite materials as photoactive layers that generate electric power when exposed to light. Some photoactive layers may be degraded by environmental factors including temperature, humidity, and oxidation. Therefore, improvements to perovskite material durability and efficiency are desirable. 
     The features and advantages of the present disclosure will be readily apparent to those skilled in the art. While numerous changes may be made by those skilled in the art, such changes are within the spirit of the invention. 
     SUMMARY 
     To address the foregoing problems with existing solutions, disclosed are enhanced perovskite materials and methods for forming such materials. 
     According to some embodiments, a perovskite material has a perovskite crystal lattice having a formula of C x M y X z , where x, y, and z, are real numbers. Bulky organic cations reside near a surface or a grain boundary of the perovskite crystal lattice. C includes one or more cations selected from the group consisting of Group 1 metals, Group 2 metals, ammonium, formamidinium, guanidinium, and ethene tetramine. M includes one or more metals each selected from the group consisting of Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr and combinations thereof. X includes one or more anions each selected from the group consisting of halides, pseudohalides, chalcogenides (tellurides, oxides, sulfides, and selenides), and combinations thereof. 
     In particular embodiments, a tail group of at least one bulky organic cations is not chemically connected to the surfaces or grain boundaries of the perovskite material. 
     In particular embodiments, the bulky organic cations reside less than 50 nm into the perovskite material crystal lattice from the surfaces or grain boundaries of the perovskite material crystal lattice. 
     In particular embodiments, the bulky organic cation is selected from the group consisting of n-butylammonium; benzylammonium; butane-1,4-diammonium; pentylammonium; hexylammonium; poly(vinylammonium); phenylethylammonium; 3-phenyl-1-propylammonium; 4-phenyl-1-butylammonium; 1,3-dimethylbutylammonium; 3,3-dimethylbutylammonium, and 1-octylammonium, and combinations thereof. 
     In particular embodiments, the bulky organic cation comprises 1-butylammonium. 
     In particular embodiments, the bulky organic cation comprises 1-hexylammonium. 
     In particular embodiments, the bulky organic cation comprises 1-octylammonium. 
     In particular embodiments, the bulky organic cation comprises benzylammonium. 
     In particular embodiments, the perovskite material crystal lattice has a cubic structure. 
     According to some embodiments, a perovskite material includes a formamidinium lead iodide perovskite material. Benzylammonium cations reside near a surface or a grain boundary of the formamidinium lead iodide perovskite material. 
     In particular embodiments, at least one benzyl group of the benzylammonium cations is not chemically connected to the grain boundaries or surfaces of the formamidinium lead iodide perovskite material. 
     In particular embodiments, the benzylammonium cations reside less than 50 nm into the formamidinium lead perovskite material from the surfaces or the grain boundaries of the formamidinium lead perovskite material. 
     In particular embodiments, the formamidinium lead iodide perovskite material has a cubic crystal structure. 
     According to some embodiments, a method for depositing a perovskite material includes depositing a lead salt precursor onto a substrate to form a lead salt thin film, depositing a bulky organic cation solution onto the lead salt thin film, depositing a second salt precursor onto the lead salt thin film to form a perovskite precursor thin film, and annealing the substrate to form a perovskite material. 
     In particular embodiments, the bulky organic cation solution comprises a bulky organic cation selected from the group consisting of n-butylammonium; benzylammonium; butane-1,4-diammonium; pentylammonium; hexylammonium; poly(vinylammonium); phenylethylammonium; 3-phenyl-1-propylammonium; 4-phenyl-1-butyl ammonium; 1,3-dimethylbutylammonium; 3,3-dimethylbutylammonium, 1-octylammonium, ammonium functionalized perylenes, and combinations thereof. 
     In particular embodiments, the bulky organic cation solution comprises 1-butylammonium. 
     In particular embodiments, the bulky organic cation solution comprises benzylammonium. 
     In particular embodiments, the bulky organic cation solution has a bulky organic cation concentration between 0.01 and 0.1 M. 
     In particular embodiments, the bulky organic cation solution has a bulky organic cation concentration between 0.03 and 0.05 M. 
     In particular embodiments, the lead salt precursor, the second salt precursor, and the bulky cation solution are deposited by spin-coating, slot-die printing, sputtering, PE-CVD, thermal evaporation, or spray coating. 
     In particular embodiments, the lead salt precursor comprises one or more lead salts selected from the group consisting of lead (II) iodide, lead (II) thiocyanate, lead (II) chloride, lead (II) bromide, and combinations thereof. 
     In particular embodiments, the lead salt precursor comprises lead (II) iodide. 
     In particular embodiments, the second salt precursor comprises formamidinium iodide, formamidinium thiocyanate, or guanidinium thiocyanate. 
     In particular embodiments, the second salt precursor comprises formamidinium iodide. 
     In particular embodiments, the lead salt precursor comprises one or more solvents selected from the group consisting of N-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone, dimethylformamide, dialkylformamide, dimethylsulfoxide (DMSO), methanol, ethanol, propanol, butanol, tetrahydrofuran, formamide, tert-butylpyridine, pyridine, alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, and combinations thereof. 
     In particular embodiments, the lead salt precursor comprises one or more additives selected from the group consisting of an amino acid, 5-aminovaleric acid hydroiodide, 1,8-diiodooctane, 1,8-dithiooctane, formamidinium halide, acetic acid, trifluoroacetic acid, a methylammonium halide, water, and combinations thereof. 
     In particular embodiments, the lead salt precursor comprises a 90:10 mole ratio of PbI 2  to PbCl 2  dissolved in anhydrous DMF. 
     In particular embodiments, annealing occurs in an atmosphere selected from the group consisting of ambient air, a controlled humidity environment, pure argon, pure nitrogen pure oxygen, pure hydrogen, pure helium, pure neon, pure krypton, pure CO 2 , and combinations thereof. 
     In particular embodiments, annealing occurs at a temperature greater than or equal to 50° C. and less than or equal to 300° C. 
     In particular embodiments, annealing in a controlled humidity environment occurs at an absolute humidity greater than or equal to 0 g H 2 O/m 3  air and less than or equal to 20 g H 2 O/m 3  air. 
     In particular embodiments, annealing in a controlled humidity environment occurs at an absolute humidity between about 4 and 7 g H 2 O/m 3  air. 
     According to some embodiments, a perovskite material includes a perovskite crystal lattice having a formula of C x M y X z , where x, y, and z, are real numbers. 1,4-diammonium butane cations are disposed within or at a surface of the perovskite crystal lattice. C comprises one or more cations selected from the group consisting of Group 1 metals, Group 2 metals, ammonium, formamidinium, guanidinium, and ethene tetramine, M comprises one or more metals each selected from the group consisting of Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr and combinations thereof, and X comprises one or more anions each selected from the group consisting of halides, pseudohalides, chalcogenides, and combinations thereof. 
     In particular embodiments, the 1,4-diammonium butane cations have a concentration between 1 mol % and 20 mol % in the perovskite material. 
     In particular embodiments, the 1,4-diammonium butane cations have a concentration between 1 mol % and 5 mol % in the perovskite material. 
     In particular embodiments, the 1,4-diammonium butane cations have a concentration of approximately 5 mol % in the perovskite material. 
     In particular embodiments, C comprises formamidinium, M comprises lead, and X comprises iodide. 
     In particular embodiments, the perovskite material crystal lattice has a cubic structure. 
     In particular embodiments, the ammonium groups of the 1,4-diammonium butane cations substitute for formamidinium ions within the perovskite crystal lattice. 
     According to some embodiments, a perovskite material includes a formamidinium lead iodide perovskite material and 1,4-diammonium butane cations disposed within or at a surface of the formamidinium lead iodide perovskite material. 
     In particular embodiments, the ammonium groups of the 1,4-diammonium butane cations substitute for formamidinium ions within the perovskite crystal lattice. 
     In particular embodiments, the 1,4-diammonium butane cations have a concentration between 1 mol % and 20 mol % in the perovskite material. 
     In particular embodiments, the 1,4-diammonium butane cations have a concentration between 1 mol % and 5 mol % in the perovskite material. 
     In particular embodiments, the 1,4-diammonium butane cations have a concentration of approximately 5 mol % in the perovskite material. 
     In particular embodiments, the formamidinium lead iodide perovskite material has a cubic crystal structure. 
     According to some embodiments, a method for depositing perovskite material includes depositing a lead salt precursor onto a substrate to form a lead salt thin film. The lead salt precursor comprises a lead salt and a 1,4-diammonium butane salt. Next, a second salt precursor may be deposited onto the lead salt thin film to form a perovskite precursor thin film. Next, the substrate and perovskite precursor thin film may be annealed to form a perovskite material. 
     In particular embodiments, the lead salt precursor has a 1,4-diammonium butane concentration between 1 mol % and 20 mol %. 
     In particular embodiments, the lead salt precursor has a 1,4-diammonium butane concentration between 1 mol % and 5 mol %. 
     In particular embodiments, the lead salt precursor has a 1,4-diammonium butane concentration of approximately 5 mol %. 
     In particular embodiments, the lead salt precursor comprises one or more lead salts selected from the group consisting of lead (II) iodide, lead (II) thiocyanate, lead (II) chloride, lead (II) bromide, and combinations thereof. 
     In particular embodiments, the lead salt precursor comprises lead (II) iodide. 
     In particular embodiments, the second salt precursor comprises a salt selected from the group consisting of formamidinium iodide, formamidinium thiocyanate, guanidinium thiocyanate, and combinations thereof. 
     In particular embodiments, the second salt precursor comprises formamidinium iodide. 
     In particular embodiments, the lead salt precursor comprises one or more solvents selected from the group consisting of N-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone, dimethylformamide, dialkylformamide, dimethylsulfoxide, methanol, ethanol, propanol, butanol, tetrahydrofuran, formamide, tert-butylpyridine, pyridine, alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, and combinations thereof. 
     In particular embodiments, the lead salt precursor comprises one or more additives selected from the group consisting of an amino acid, 5-aminovaleric acid hydroiodide, 1,8-diiodooctane, 1,8-dithiooctane, formamidinium halide, acetic acid, trifluoroacetic acid, a methylammonium halide, water, and combinations thereof. 
     In particular embodiments, the lead salt precursor comprises a 90:10 mole ratio of PbI 2  to PbCl 2  dissolved in anhydrous dimethylformamide. 
     In particular embodiments, annealing occurs in an atmosphere selected from the group consisting of ambient air, a controlled humidity environment, pure argon, pure nitrogen pure oxygen, pure hydrogen, pure helium, pure neon, pure krypton, pure CO 2 , and combinations thereof. 
     In particular embodiments, annealing occurs at a temperature greater than or equal to 50° C. and less than or equal to 300° C. 
     In particular embodiments, annealing in a controlled humidity environment occurs at an absolute humidity greater than or equal to 0 g H 2 O/m 3  air and less than or equal to 20 g H 2 O/m 3  air. 
     In particular embodiments, annealing in a controlled humidity environment occurs at an absolute humidity between about 4 and 7 g H 2 O/m 3  air. 
     According to some embodiments, a method for depositing perovskite material includes depositing a lead salt precursor onto a substrate to form a lead salt thin film. Next, a 1,4-diammonium butane salt precursor is deposited onto the lead salt thin film. Next, a third salt precursor may be deposited onto the lead salt thin film to form a perovskite precursor thin film. Next, the substrate and perovskite precursor thin film may be annealed to form a perovskite material. 
     In particular embodiments, the lead salt precursor has a 1,4-diammonium butane concentration between 1 mol % and 5 mol %. 
     In particular embodiments, the lead salt precursor comprises lead (II) iodide and the third salt precursor comprises formamidinium iodide. 
     In particular embodiments, the lead salt precursor comprises a 90:10 mole ratio of PbI 2  to PbCl 2  dissolved in anhydrous dimethylformamide and comprises as much as 10 mol % cesium. Annealing occurs at a temperature greater than or equal to 50° C. and less than or equal to 300° C. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic view of a typical photovoltaic cell including an active layer according to some embodiments of the present disclosure. 
         FIG.  2    is a stylized diagram showing components of an example PV device according to some embodiments of the present disclosure. 
         FIG.  3    is a stylized diagram showing components of an example device according to some embodiments of the present disclosure. 
         FIG.  4    is a stylized diagram showing components of an example device according to some embodiments of the present disclosure. 
         FIG.  5    is a stylized diagram showing an illustration of a Ruddlesden-Popper perovskite. 
         FIG.  6    is a stylized diagram showing an illustration of a perovskite material with addition of an alkyl ammonium cation according to some embodiments of the present disclosure. 
         FIG.  7    is a stylized diagram showing an illustration of a perovskite material with a 1-butylammonium surface layer according to some embodiments of the present disclosure. 
         FIG.  8    is a stylized diagram showing an illustration of a perovskite material with a surface layer of multiple bulky organic cations according to some embodiments of the present disclosure. 
         FIG.  8 A  is a stylized diagram showing an illustration of a perovskite material with a surface layer of multiple bulky organic cations according to some embodiments of the present disclosure. 
         FIG.  9    is an illustration of a comparison of images taken of a perovskite material with and without a 1-butylammonium (“BAI”) surface coating according to some embodiments of the present disclosure. 
         FIG.  10    is a stylized diagram showing an illustration of a comparison of images taken of a perovskite material with and without a 1-butylammonium (“BAI”) surface coating according to some embodiments of the present disclosure. 
         FIGS.  11 A-D  illustrate various perylene monoimides and diimides that may be applied to the surface of a perovskite material according to some embodiments of the present disclosure. 
         FIG.  12    is a stylized diagram showing an illustration of a perovskite material with addition of a perylene monoimides ammonium cation according to some embodiments of the present disclosure. 
         FIG.  13    is a stylized diagram showing an illustration of 1,4-diammonium butane incorporated into the crystal lattice of a formamidinium lead iodide perovskite material according to some embodiments of the present disclosure. 
         FIG.  14    is an illustration of x-ray diffraction peaks (XRD) for perovskite having various concentrations of 1,4-diammonium butane according to some embodiments of the present disclosure. 
         FIG.  15    provides images of perovskite material samples having various concentrations of 1,4-diammonium butane over time according to some embodiments of the present disclosure. 
         FIG.  16    provides illustrations of poly-ammonium alkyl cations, according to some embodiments of the present disclosure. 
         FIG.  16 A  is a stylized diagram showing an illustration of 1,8 diammonium octane incorporated into the crystal lattice of a formamidinium lead iodide perovskite material according to some embodiments of the present disclosure. 
         FIG.  16 B  is a stylized diagram showing an illustration of bis(4-aminobutyl)-ammonium incorporated into the crystal lattice of a formamidinium lead iodide perovskite material according to some embodiments of the present disclosure. 
         FIG.  16 C  is a stylized diagram showing an illustration of tris(4-aminobutyl)-ammonium incorporated into the crystal lattice of a formamidinium lead iodide perovskite material according to some embodiments of the present disclosure. 
         FIGS.  17 - 28    provide illustrations of the structures of certain organic molecules, according to some embodiments of the present disclosure. 
         FIG.  29    illustrates x-ray diffraction patterns of perovskites materials according to some embodiments of the present disclosure. 
         FIG.  30    provides a stylized illustration of thicknesses of inorganic metal halide sublattices of perovskite materials according to some embodiments of the present disclosure. 
         FIG.  31    shows optical and photoluminescence images of perovskite material photovoltaic devices according to some embodiments of the present disclosure. 
         FIG.  32    illustrates power output curves of perovskite material photovoltaic devices according to some embodiments of the present disclosure. 
         FIG.  33    illustrates current-voltage (I-V) scans of perovskite material photovoltaic devices according to some embodiments of the present disclosure. 
         FIG.  34    illustrates box plots for open-circuit voltage (Voc), short-circuit current density (Jsc), Fill Factor (FF) and power conversion efficiency (PCE) for perovskite material photovoltaic devices according to some embodiments of the present disclosure. 
         FIG.  35    illustrates external quantum efficiency (EQE) curves of perovskite material photovoltaic devices according to some embodiments of the present disclosure. 
         FIG.  36    shows admittance spectroscopy plots of perovskite material photovoltaic devices according to some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Improvements in various aspects of PV technologies compatible with organic, non-organic, and/or hybrid PVs promise to further lower the cost of both organic PVs and other PVs. For example, some solar cells, such as perovskite PV solar cells, may take advantage of novel cost-effective and high-stability alternative components, such as nickel oxide interfacial layers. In addition, various kinds of solar cells may advantageously include chemical additives and other materials that may, among other advantages, be more cost-effective and durable than conventional options currently in existence. 
     The present disclosure relates generally to compositions of matter, apparatus and methods of use of materials in photovoltaic cells in creating electrical energy from solar radiation. More specifically, this disclosure relates to photoactive and other compositions of matter, as well as apparatus, methods of use, and formation of such compositions of matter. 
     Some or all of materials in accordance with some embodiments of the present disclosure may also advantageously be used in any organic or other electronic device, with some examples including, but not limited to: batteries, field-effect transistors (FETs), light-emitting diodes (LEDs), non-linear optical devices, memristors, capacitors, rectifiers, and/or rectifying antennas. 
     In some embodiments, the present disclosure may provide PV and other similar devices (e.g., batteries, hybrid PV batteries, multi junction PVs, FETs, LEDs, x-ray detectors, gamma ray detectors, photodiodes, CCDs, etc.). Such devices may in some embodiments include improved active material, interfacial layers (IFLs), and/or one or more perovskite materials. A perovskite material may be incorporated into various of one or more aspects of a PV or other device. A perovskite material according to some embodiments may be of the general formula CMX 3 , where: C comprises one or more cations (e.g., an amine, ammonium, phosphonium, a Group 1 metal, a Group 2 metal, and/or other cations or cation-like compounds); M comprises one or more metals (examples including Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr); and X comprises one or more anions. Perovskite materials according to various embodiments are discussed in greater detail below. 
     Photovoltaic Cells and Other Electronic Devices 
     Some PV embodiments may be described by reference to the illustrative depictions of solar cells as shown in  FIG.  1   . An example PV architecture according to some embodiments may be substantially of the form substrate-anode-IFL-active layer-IFL-cathode. The active layer of some embodiments may be photoactive, and/or it may include photoactive material. Other layers and materials may be utilized in the cell as is known in the art. Furthermore, it should be noted that the use of the term “active layer” is in no way meant to restrict or otherwise define, explicitly or implicitly, the properties of any other layer—for instance, in some embodiments, either or both IFLs may also be active insofar as they may be semiconducting. In particular, referring to  FIG.  1   , a stylized generic PV cell  1000  is depicted, illustrating the highly interfacial nature of some layers within the PV. The PV  1000  represents a generic architecture applicable to several PV devices, such as perovskite material PV embodiments. The PV cell  1000  includes a transparent substrate layer  1010 , which may be glass (or a material similarly transparent to solar radiation) which allows solar radiation to transmit through the layer. The transparent layer of some embodiments may also be referred to as a superstrate or substrate (e.g., as with substrate layer  3901  of  FIG.  2   ), and it may comprise any one or more of a variety of rigid or flexible materials such as: glass, polyethylene, polypropylene, polycarbonate, polyimide, PMMA, PET, PEN, Kapton, or quartz. In general, the term substrate is used to refer to material upon which the device is deposited during manufacturing. The photoactive layer  1040  may be composed of electron donor or p-type material, and/or an electron acceptor or n-type material, and/or an ambipolar semiconductor, which exhibits both p- and n-type material characteristics, and/or an intrinsic semiconductor which exhibits neither n-type or p-type characteristics. Photoactive layer  1040  may be a perovskite material as described herein, in some embodiments. The active layer or, as depicted in  FIG.  1   , the photo-active layer  1040 , is sandwiched between two electrically conductive electrode layers  1020  and  1060 . In  FIG.  1   , the electrode layer  1020  may be a transparent conductor such as a tin-doped indium oxide (ITO material) or other material as described herein. In other embodiments second substrate  1070  and second electrode  1060  may be transparent. As previously noted, an active layer of some embodiments need not necessarily be photoactive, although in the device shown in  FIG.  1   , it is. The electrode layer  1060  may be an aluminum material or other metal, or other conductive materials such as carbon. Other materials may be used as is known in the art. The cell  1010  also includes an interfacial layer (IFL)  1030 , shown in the example of  FIG.  1   . The IFL may assist in charge separation. In other embodiments, the IFL  1030  may comprise a multi-layer IFL, which is discussed in greater detail below. There also may be an IFL  1050  adjacent to electrode  1060 . In some embodiments, the IFL  1050  adjacent to electrode  1060  may also or instead comprise a multi-layer IFL (again, discussed in greater detail below). An IFL according to some embodiments may be semiconducting in character and may be either intrinsic, ambipolar, p-type, or n-type, or it may be dielectric in character. In some embodiments, the IFL on the cathode side of the device (e.g., IFL  1050  as shown in  FIG.  1   ) may be p-type, and the IFL on the anode side of the device (e.g., IFL  1030  as shown in  FIG.  1   ) may be n-type. In other embodiments, however, the cathode-side IFL may be n-type and the anode-side IFL may be p-type. The cell  1010  may be attached to electrical leads by electrodes  1060  and  1020  and a discharge unit, such as a battery, motor, capacitor, electric grid, or any other electrical load. 
     Various embodiments of the present disclosure provide improved materials and/or designs in various aspects of solar cell and other devices, including among other things, active materials (including hole-transport and/or electron-transport layers), interfacial layers, and overall device design. 
     Interfacial Layers 
     The present disclosure, in some embodiments, provides advantageous materials and designs of one or more interfacial layers within a PV, including thin-coat IFLs. Thin-coat IFLs may be employed in one or more IFLs of a PV according to various embodiments discussed herein. 
     According to various embodiments, devices may optionally include an interfacial layer between any two other layers and/or materials, although devices need not contain any interfacial layers. For example, a perovskite material device may contain zero, one, two, three, four, five, or more interfacial layers (such as the example device of  FIG.  2   , which contains five interfacial layers  3903 ,  3905 ,  3907 ,  3909 , and  3911 ). An interfacial layer may include any suitable material for enhancing charge transport and/or collection between two layers or materials; it may also help prevent or reduce the likelihood of charge recombination once a charge has been transported away from one of the materials adjacent to the interfacial layer. An interfacial layer may additionally physically and electrically homogenize its substrates to create variations in substrate roughness, dielectric constant, adhesion, creation or quenching of defects (e.g., charge traps, surface states). Suitable interfacial materials may include any one or more of: Ag; Al; Au; B; Bi; Ca; Cd; Ce; Co; Cu; Fe; Ga; Ge; H; In; Mg; Mn; Mo; Nb; Ni; Pt; Sb; Sc; Si; Sn; Ta; Ti; V; W; Y; Zn; Zr; carbides of any of the foregoing metals (e.g., SiC, Fe 3 C, WC, VC, MoC, NbC); silicides of any of the foregoing metals (e.g., Mg 2 Si, SrSi 2 , Sn 2 Si); oxides of any of the foregoing metals (e.g., alumina, silica, titania, SnO 2 , ZnO, NiO, ZrO 2 , HfO 2 ), include transparent conducting oxides (“TCOs”) such as indium tin oxide, aluminum doped zinc oxide (AZO), cadmium oxide (CdO), and fluorine doped tin oxide (FTO); sulfides of any of the foregoing metals (e.g., CdS, MoS 2 , SnS 2 ); nitrides of any of the foregoing metals (e.g., GaN, Mg 3 N 2 , TiN, BN, Si 3 N 4 ); selenides of any of the foregoing metals (e.g., CdSe, FeS 2 , ZnSe); tellurides of any of the foregoing metals (e.g., CdTe, TiTe 2 , ZnTe); phosphides of any of the foregoing metals (e.g., InP, GaP, GaInP); arsenides of any of the foregoing metals (e.g., CoAs 3 , GaAs, InGaAs, NiAs); antimonides of any of the foregoing metals (e.g., AlSb, GaSb, InSb); halides of any of the foregoing metals (e.g., CuCl, CuI, BiI 3 ); pseudohalides of any of the foregoing metals (e.g., CuSCN, AuCN, Fe(SCN) 2 ); carbonates of any of the foregoing metals (e.g., CaCO 3 , Ce 2 (CO 3 ) 3 ); functionalized or non-functionalized alkyl silyl groups; graphite; graphene; fullerenes; carbon nanotubes; any mesoporous material and/or interfacial material discussed elsewhere herein; and combinations thereof (including, in some embodiments, bilayers, trilayers, or multi-layers of combined materials). In some embodiments, an interfacial layer may include perovskite material. Further, interfacial layers may comprise doped embodiments of any interfacial material mentioned herein (e.g., Y-doped ZnO, N-doped single-wall carbon nanotubes). Interfacial layers may also comprise a compound having three of the above materials (e.g., CuTiO 3 , Zn 2 SnO 4 ) or a compound having four of the above materials (e.g., CoNiZnO). The materials listed above may be present in a planar, mesoporous or otherwise nano-structured form (e.g. rods, spheres, flowers, pyramids), or aerogel structure. 
     First, as previously noted, one or more IFLs (e.g., either or both IFLs  2626  and  2627  as shown in  FIG.  1   ) may comprise a photoactive organic compound of the present disclosure as a self-assembled monolayer (SAM) or as a thin film. When a photoactive organic compound of the present disclosure is applied as a SAM, it may comprise a binding group through which it may be covalently or otherwise bound to the surface of either or both of the anode and cathode. The binding group of some embodiments may comprise any one or more of COOH, SiX 3  (where X may be any moiety suitable for forming a ternary silicon compound, such as Si(OR) 3  and SiCl 3 ), SO 3 , POOH, OH, CH 2 X (where X may comprise a Group 17 halide), and O. The binding group may be covalently or otherwise bound to an electron-withdrawing moiety, an electron donor moiety, and/or a core moiety. The binding group may attach to the electrode surface in a manner so as to form a directional, organized layer of a single molecule (or, in some embodiments, multiple molecules) in thickness (e.g., where multiple photoactive organic compounds are bound to the anode and/or cathode). As noted, the SAM may attach via covalent interactions, but in some embodiments, it may attach via ionic, hydrogen-bonding, and/or dispersion force (i,e., Van Der Waals) interactions. Furthermore, in certain embodiments, upon light exposure, the SAM may enter into a zwitterionic excited state, thereby creating a highly-polarized IFL, which may direct charge carriers from an active layer into an electrode (e.g., either the anode or cathode). This enhanced charge-carrier injection may, in some embodiments, be accomplished by electronically poling the cross-section of the active layer and therefore increasing charge-carrier drift velocities towards their respective electrode (e.g., hole to anode; electrons to cathode). Molecules for anode applications of some embodiments may comprise tunable compounds that include a primary electron donor moiety bound to a core moiety, which in turn is bound to an electron-withdrawing moiety, which in turn is bound to a binding group. In cathode applications according to some embodiments, IFL molecules may comprise a tunable compound comprising an electron poor moiety bound to a core moiety, which in turn is bound to an electron donor moiety, which in turn is bound to a binding group. When a photoactive organic compound is employed as an IFL according to such embodiments, it may retain photoactive character, although in some embodiments it need not be photoactive. 
     Metal oxides may be used in thin film IFLs of some embodiments and may include semiconducting metal oxides, such as NiO, SnO 2 WO 3 , V 2 O 5 , or MoO 3 . The embodiment wherein the second (e.g., n-type) active material comprises TiO 2  coated with a thin-coat IFL comprising Al 2 O 3  could be formed, for example, with a precursor material such as Al(NO 3 ) 3 .xH 2 O, or any other material suitable for depositing Al 2 O 3  onto the TiO 2 , followed by thermal annealing and dye coating. In example embodiments wherein a MoO 3  coating is instead used, the coating may be formed with a precursor material such as Na 2 Mo 4 .2H 2 O; whereas a V 2 O 5  coating according to some embodiments may be formed with a precursor material such as NaVO 3 ; and a WO 3  coating according to some embodiments may be formed with a precursor material such as NaWO 4 .H 2 O. The concentration of precursor material (e.g., Al(NO 3 ) 3 .xH 2 O) may affect the final film thickness (here, of Al 2 O 3 ) deposited on the TiO 2  or other active material. Thus, modifying the concentration of precursor material may be a method by which the final film thickness may be controlled. For example, greater film thickness may result from greater precursor material concentration. Greater film thickness may not necessarily result in greater PCE in a PV device comprising a metal oxide coating. Thus, a method of some embodiments may include coating a TiO 2  (or other mesoporous) layer using a precursor material having a concentration in the range of approximately 0.5 to 10.0 mM; other embodiments may include coating the layer with a precursor material having a concentration in the range of approximately 2.0 to 6.0 mM; or, in other embodiments, approximately 2.5 to 5.5 mM. 
     Furthermore, although referred to herein as Al 2 O 3  and/or alumina, it should be noted that various ratios of aluminum and oxygen may be used in forming alumina. Thus, although some embodiments discussed herein are described with reference to Al 2 O 3 , such description is not intended to define a required ratio of aluminum in oxygen. Rather, embodiments may include any one or more aluminum-oxide compounds, each having an aluminum oxide ratio according to Al x O y , where x may be any value, integer or non-integer, between approximately 1 and 100. In some embodiments, x may be between approximately 1 and 3 (and, again, need not be an integer). Likewise, y may be any value, integer or non-integer, between 0.1 and 100. In some embodiments, y may be between 2 and 4 (and, again, need not be an integer). In addition, various crystalline forms of Al x O y  may be present in various embodiments, such as alpha, gamma, and/or amorphous forms of alumina. 
     Likewise, although referred to herein as NiO, MoO 3 , WO 3 , and V 2 O 5 , such compounds may instead or in addition be represented as Ni x O y Mo x O y , W x O y , and V x O y , respectively. Regarding each of Mo x O y  and W x O y , x may be any value, integer or non-integer, between approximately 0.5 and 100; in some embodiments, it may be between approximately 0.5 and 1.5. Likewise, y may be any value, integer or non-integer, between approximately 1 and 100. In some embodiments, y may be any value between approximately 1 and 4. Regarding V x O y , x may be any value, integer or non-integer, between approximately 0.5 and 100; in some embodiments, it may be between approximately 0.5 and 1.5. Likewise, y may be any value, integer or non-integer, between approximately 1 and 100; in certain embodiments, it may be an integer or non-integer value between approximately 1 and 10. In some embodiments, x and y may have values so as to be in a non-stoichiometric ratio. 
     In some embodiments, the IFL may comprise a titanate. A titanate according to some embodiments may be of the general formula M′TiO 3 , where M′ comprises any 2+ cation. In some embodiments, M′ may comprise a cationic form of Be, Mg, Ca, Sr, Ba, Ni, Zn, Cd, Hg, Cu, Pd, Pt, Sn, or Pb. In some embodiments, the IFL may comprise a single species of titanate, which in other embodiments, the IFL may comprise two or more different species of titanates. In one embodiment, the titanate has the formula SrTiO 3 . In another embodiment, the titanate may have the formula BaTiO 3 . In yet another embodiment, the titanate may have the formula CaTiO 3 . 
     By way of explanation, and without implying any limitation, titanates have a perovskite crystalline structure and strongly seed the perovskite material (e.g., methylammonium lead iodide (MAPbI 3 ), and formamidinium lead iodide (FAPbI 3 )) growth conversion process. Titanates generally also meet other IFL requirements, such as ferroelectric behavior, sufficient charge carrier mobility, optical transparency, matched energy levels, and high dielectric constant. 
     In other embodiments, the IFL may comprise a zirconate. A zirconate according to some embodiments may be of the general formula M′ZrO 3 , where M′ comprises any 2+ cation. In some embodiments, M′ may comprise a cationic form of Be, Mg, Ca, Sr, Ba, Ni, Zn, Cd, Hg, Cu, Pd, Pt, Sn, or Pb. In some embodiments, the IFL may comprise a single species of zirconate, which in other embodiments, the IFL may comprise two or more different species of zirconate. In one embodiment, the zirconate has the formula SrZrO 3 . In another embodiment, the zirconate may have the formula BaZrO 3 . In yet another embodiment, the zirconate may have the formula CaZrO 3 . 
     By way of explanation, and without implying any limitation, zirconates have a perovskite crystalline structure and strongly seed the perovskite material (e.g., MAPbI 3 , FAPbI 3 ) growth conversion process. Zirconates generally also meet other IFL requirements, such as ferroelectric behavior, sufficient charge carrier mobility, optical transparency, matched energy levels, and high dielectric constant. 
     In other embodiments, the IFL may comprise a stannate. A stannate according to some embodiments may be of the general formula M′SnO 3 , or M′ 2 SnO 4  where M′ comprises any 2+ cation. In some embodiments, M′ may comprise a cationic form of Be, Mg, Ca, Sr, Ba, Ni, Zn, Cd, Hg, Cu, Pd, Pt, Sn, or Pb. In some embodiments, the IFL may comprise a single species of stannate, which in other embodiments, the IFL may comprise two or more different species of stannate. In one embodiment, the stannate has the formula SrSnO 3 . In another embodiment, the stannate may have the formula BaSnO 3 . In yet another embodiment, the stannate may have the formula CaSnO 3 . 
     By way of explanation, and without implying any limitation, stannates have a perovskite crystalline structure and strongly seed the perovskite material (e.g., MAPbI 3 , FAPbI 3 ) growth conversion process. Stannates generally also meet other IFL requirements, such as ferroelectric behavior, sufficient charge carrier mobility, optical transparency, matched energy levels, and high dielectric constant. 
     In other embodiments, the IFL may comprise a plumbate. A plumbate according to some embodiments may be of the general formula M′PbO 3 , where M′ comprises any 2+ cation. In some embodiments, M′ may comprise a cationic form of Be, Mg, Ca, Sr, Ba, Ni, Zn, Cd, Hg, Cu, Pd, Pt, Sn, or Pb. In some embodiments, the IFL may comprise a single species of plumbate, which in other embodiments, the IFL may comprise two or more different species of plumbate. In one embodiment, the plumbate has the formula SrPbO 3 . In another embodiment, the plumbate may have the formula BaPbO 3 . In yet another embodiment, the plumbate may have the formula CaPbO 3 . In yet another embodiment, the plumbate may have the formula Pb II Pb IV O 3 . 
     By way of explanation, and without implying any limitation, plumbate s have a perovskite crystalline structure and strongly seed the perovskite material (e.g., MAPbI 3 , FAPbI 3 ) growth conversion process. Plumbates generally also meet other IFL requirements, such as ferroelectric behavior, sufficient charge carrier mobility, optical transparency, matched energy levels, and high dielectric constant. 
     Further, in other embodiments, an IFL may comprise a combination of a zirconate and a titanate in the general formula M′[ Zr   x   Ti   1-x ]O 3 , where X is greater than 0 but less than one 1, and M′ comprises any 2+ cation. In some embodiments, M′ may comprise a cationic form of Be, Mg, Ca, Sr, Ba, Ni, Zn, Cd, Hg, Cu, Pd, Pt, Sn, or Pb. In some embodiments, the IFL may comprise a single species of zirconate, which in other embodiments, the IFL may comprise two or more different species of zirconate. In one embodiment, the zirconate/titanate combination has the formula Pb[ Zr   x   Ti   1-x ]O 3 . In another embodiment, the zirconate/titanate combination has the formula Pb[ Zr   0.52   Ti   0.48 ]O 3 . 
     By way of explanation, and without implying any limitation, a zirconate/titanate combination have a perovskite crystalline structure and strongly seed the perovskite material (e.g., MAPbI 3 , FAPbI 3 ) growth conversion process. Zirconate/titanate combinations generally also meet other IFL requirements, such as ferroelectric behavior, sufficient charge carrier mobility, optical transparency, matched energy levels, and high dielectric constant. 
     In other embodiments, the IFL may comprise a niobate. A niobate according to some embodiments may be of the general formula M′NbO 3 , where: M′ comprises any 1+ cation. In some embodiments, M′ may comprise a cationic form of Li, Na, K, Rb, Cs, Cu, Ag, Au, Tl, ammonium, or H. In some embodiments, the IFL may comprise a single species of niobate, which in other embodiments, the IFL may comprise two or more different species of niobate. In one embodiment, the niobate has the formula LiNbO 3 . In another embodiment, the niobate may have the formula NaNbO 3 . In yet another embodiment, the niobate may have the formula AgNbO 3 . 
     By way of explanation, and without implying any limitation, niobates generally meet IFL requirements, such as piezoelectric behavior, non-linear optical polarizability, photoelasticity, ferroelectric behavior, Pockels effect, sufficient charge carrier mobility, optical transparency, matched energy levels, and high dielectric constant. 
     In one embodiment, a perovskite material device may be formulated by casting PbI 2  onto a SrTiO 3 -coated ITO substrate. The PbI 2  may be converted to MAPbI 3  by a dipping process. This process is described in greater detail below. This resulting conversion of PbI 2  to MAPbI 3  is more complete (as observed by optical spectroscopy) as compared to the preparation of the substrate without SrTiO 3 . 
     Any interfacial material discussed herein may further comprise doped compositions. To modify the characteristics (e.g., electrical, optical, mechanical) of an interfacial material, a stoichiometric or non-stoichiometric material may be doped with one or more elements (e.g., Na, Y, Mg, N, P) in amounts ranging from as little as 1 ppb to 50 mol %. Some examples of interfacial materials include: NiO, TiO 2 , SrTiO 3 , Al 2 O 3 , ZrO 2 , WO 3 , V 2 O 5 , MO 3 , ZnO, graphene, and carbon black. Examples of possible dopants for these interfacial materials include: Li, Na, Be, Mg, Ca, Sr, Ba, Sc, Y, Nb, Ti, Fe, Co, Ni, Cu, Ga, Sn, In, B, N, P, C, S, As, a halide, a pseudohalide (e.g., cyanide, cyanate, isocyanate, fulminate, thiocyanate, isothiocyanate, azide, tetracarbonylcobaltate, carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide, and tricyanomethanide), and Al in any of its oxidation states. References herein to doped interfacial materials are not intended to limit the ratios of component elements in interfacial material compounds. 
     In some embodiments, multiple IFLs made from different materials may be arranged adjacent to each other to form a composite IFL. This configuration may involve two different IFLs, three different IFLs, or an even greater number of different IFLs. The resulting multi-layer IFL or composite IFL may be used in lieu of a single-material IFL. For example, a composite IFL may be used any IFL shown in the example of  FIG.  2   , such as IFL  3903 , IFL  3905 , IFL  3907 , IFL  3909 , or IFL  3911 . While the composite IFL differs from a single-material IFL, the assembly of a perovskite material PV cell having multi-layer IFLs is not substantially different than the assembly of a perovskite material PV cell having only single-material IFLs. 
     Generally, the composite IFL may be made using any of the materials discussed herein as suitable for an IFL. In one embodiment, the IFL comprises a layer of Al 2 O 3  and a layer of ZnO or M:ZnO (doped ZnO, e.g., Be:ZnO, Mg:ZnO, Ca:ZnO, Sr:ZnO, Ba:ZnO, Sc:ZnO, Y:ZnO, Nb:ZnO). In an embodiment, the IFL comprises a layer of ZrO 2  and a layer of ZnO or M:ZnO. In certain embodiments, the IFL comprises multiple layers. In some embodiments, a multi-layer IFL generally has a conductor layer, a dielectric layer, and a semi-conductor layer. In particular embodiments the layers may repeat, for example, a conductor layer, a dielectric layer, a semi-conductor layer, a dielectric layer, and a semi-conductor layer. Examples of multi-layer IFLs include an IFL having an ITO layer, an Al 2 O 3  layer, a ZnO layer, and a second Al 2 O 3  layer; an IFL having an ITO layer, an Al 2 O 3  layer, a ZnO layer, a second Al 2 O 3  layer, and a second ZnO layer; an IFL having an ITO layer, an Al 2 O 3  layer, a ZnO layer, a second Al 2 O 3  layer, a second ZnO layer, and a third Al 2 O 3  layer; and IFLs having as many layers as necessary to achieve the desired performance characteristics. As discussed previously, references to certain stoichiometric ratios are not intended to limit the ratios of component elements in IFL layers according to various embodiments. 
     Arranging two or more adjacent IFLs as a composite IFL may outperform a single IFL in perovskite material PV cells where attributes from each IFL material may be leveraged in a single IFL. For example, in the architecture having an ITO layer, an Al 2 O 3  layer, and a ZnO layer, where ITO is a conducting electrode, Al 2 O 3  is a dielectric material and ZnO is a n-type semiconductor, ZnO acts as an electron acceptor with well performing electron transport properties (e.g., mobility). Additionally, Al 2 O 3  is a physically robust material that adheres well to ITO, homogenizes the surface by capping surface defects (e.g., charge traps), and improves device diode characteristics through suppression of dark current. 
     Additionally, some perovskite material PV cells may include so called “tandem” PV cells having more than one perovskite photoactive layer. For example, both photoactive materials  3908  and  3906  of  FIG.  2    may be perovskite materials. In such tandem PV cells an interfacial layer between the two photoactive layers, such as IFL  3907  of  FIG.  2    may comprise a multi-layer, or composite, IFL. In some embodiments, the layers sandwiched between the two photoactive layers of a tandem PV device may include an electrode layer. 
     A tandem PV device may include the following layers, listed in order from either top to bottom or bottom to top: a first substrate, a first electrode, a first interfacial layer, a first perovskite material, a second interfacial layer, a second electrode, a third interfacial layer, a second perovskite material, a fourth interfacial layer, and a third electrode. In some embodiments, the first and third interfacial layers may be hole transporting interfacial layers and the second and fourth interfacial layers may be electron transporting interfacial layers. In other embodiments, the first and third interfacial layers may be electron transporting interfacial layers and the second and fourth interfacial layers may be hole transporting interfacial layers. In yet other embodiments, the first and fourth interfacial layers may be hole transporting interfacial layers and the second and third interfacial layers may be electron transporting interfacial layers. In other embodiments, the first and fourth interfacial layers may be electron transporting interfacial layers and the second and third interfacial layers may be hole transporting interfacial layers. In tandem PV devices the first and second perovskite materials may have different band gaps. In some embodiments, the first perovskite material may be formamidinium lead bromide (FAPbBr 3 ) and the second perovskite material may be formamidinium lead iodide (FAPbI 3 ). In other embodiments, the first perovskite material may be methylammonium lead bromide (MAPbBr 3 ) and the second perovskite material may be formamidinium lead iodide (FaPbI 3 ). In other embodiments, the first perovskite material may be methylammonium lead bromide (MAPbBr 3 ) and the second perovskite material may be methylammonium lead iodide (MAPbI 3 ). 
     Perovskite Material 
     A perovskite material may be incorporated into one or more aspects of a PV or other device. A perovskite material according to some embodiments may be of the general formula C x M y X z , where: C comprises one or more cations (e.g., an amine, ammonium, phosphonium a Group 1 metal, a Group 2 metal, and/or other cations or cation-like compounds); M comprises one or more metals (examples including Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr); X comprises one or more anions; and w, y, and z represent real numbers between 1 and 20. In some embodiments, C may include one or more organic cations. In some embodiments, each organic cation C may be larger than each metal M, and each anion X may be capable of bonding with both a cation C and a metal M. In particular embodiments, a perovskite material may be of the formula CMX 3 . 
     In certain embodiments, C may include an ammonium, an organic cation of the general formula [NR 4 ] +  where the R groups may be the same or different groups. Suitable R groups include, but are not limited to: hydrogen, methyl, ethyl, propyl, butyl, pentyl group or isomer thereof; any alkane, alkene, or alkyne CxHy, where x=1-20, y=1-42, cyclic, branched or straight-chain; alkyl halides, CxHyX z , x=1-20, y=0-42, z=1-42, X═F, Cl, Br, or I; any aromatic group (e.g., phenyl, alkylphenl, alkoxyphenyl, pyridine, naphthalene); cyclic complexes where at least one nitrogen is contained within the ring (e.g., pyridine, pyrrole, pyrrolidine, piperidine, tetrahydroquinoline); any sulfur-containing group (e.g., sulfoxide, thiol, alkyl sulfide); any nitrogen-containing group (nitroxide, amine); any phosphorous containing group (phosphate); any boron-containing group (e.g., boronic acid); any organic acid (e.g., acetic acid, propanoic acid); and ester or amide derivatives thereof; any amino acid (e.g., glycine, cysteine, proline, glutamic acid, arginine, serine, histidine, 5-ammoniumvaleric acid) including alpha, beta, gamma, and greater derivatives; any silicon containing group (e.g., siloxane); and any alkoxy or group, —OCxHy, where x=0-20, y=1-42. 
     In certain embodiments, C may include a formamidinium, an organic cation of the general formula [R 2 NCRNR 2 ] +  where the R groups may be the same or different groups. Suitable R groups include, but are not limited to: hydrogen, methyl, ethyl, propyl, butyl, pentyl group or isomer thereof; any alkane, alkene, or alkyne CxHy, where x=1-20, y=1-42, cyclic, branched or straight-chain; alkyl halides, CxHyX z , x=1-20, y=0-42, z=1-42, X═F, Cl, Br, or I; any aromatic group (e.g., phenyl, alkylphenl, alkoxyphenyl, pyridine, naphthalene); cyclic complexes where at least one nitrogen is contained within the ring (e.g., imidazole, benzimidazole, pyrimidine, (azolidinylidenemethyl)pyrrolidine, triazole); any sulfur-containing group (e.g., sulfoxide, thiol, alkyl sulfide); any nitrogen-containing group (nitroxide, amine); any phosphorous containing group (phosphate); any boron-containing group (e.g., boronic acid); any organic acid (acetic acid, propanoic acid) and ester or amide derivatives thereof; any amino acid (e.g., glycine, cysteine, proline, glutamic acid, arginine, serine, histidine, 5-ammoniumvaleric acid) including alpha, beta, gamma, and greater derivatives; any silicon containing group (e.g., siloxane); and any alkoxy or group, —OCxHy, where x=0-20, y=1-42. 
     
       
         
         
             
             
         
       
     
     Formula 1 illustrates the structure of a formamidinium cation having the general formula of [R 2 NCRNR 2 ] +  as described above. Formula 2 illustrates examples structures of several formamidinium cations that may serve as a cation “C” in a perovskite material. 
     
       
         
         
             
             
         
       
     
     In certain embodiments, C may include a guanidinium, an organic cation of the general formula [(R 2 N) 2 C═NR 2 ] +  where the R groups may be the same or different groups. Suitable R groups include, but are not limited to: hydrogen, methyl, ethyl, propyl, butyl, pentyl group or isomer thereof; any alkane, alkene, or alkyne CxHy, where x=1-20, y=1-42, cyclic, branched or straight-chain; alkyl halides, CxHyX z , x=1-20, y=0-42, z=1-42, X═F, Cl, Br, or I; any aromatic group (e.g., phenyl, alkylphenl, alkoxyphenyl, pyridine, naphthalene); cyclic complexes where at least one nitrogen is contained within the ring (e.g., octahydropyrimido[1,2-a]pyrimidine, pyrimido[1,2-a]pyrimidine, hexahydroimidazo[1,2-a]imidazole, hexahydropyrimidin-2-imine); any sulfur-containing group (e.g., sulfoxide, thiol, alkyl sulfide); any nitrogen-containing group (nitroxide, amine); any phosphorous containing group (phosphate); any boron-containing group (e.g., boronic acid); any organic acid (acetic acid, propanoic acid) and ester or amide derivatives thereof; any amino acid (e.g., glycine, cysteine, proline, glutamic acid, arginine, serine, histidine, 5-ammoniumvaleric acid) including alpha, beta, gamma, and greater derivatives; any silicon containing group (e.g., siloxane); and any alkoxy or group, —OCxHy, where x=0-20, y=1-42. 
     
       
         
         
             
             
         
       
     
     Formula 3 illustrates the structure of a guanidinium cation having the general formula of [(R 2 N) 2 C═NR 2 ] +  as described above. Formula 4 illustrates examples of structures of several guanidinium cations that may serve as a cation “C” in a perovskite material. 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In certain embodiments, C may include an ethene tetramine cation, an organic cation of the general formula [(R 2 N) 2 C═C(NR 2 ) 2 ] +  where the R groups may be the same or different groups. Suitable R groups include, but are not limited to: hydrogen, methyl, ethyl, propyl, butyl, pentyl group or isomer thereof; any alkane, alkene, or alkyne CxHy, where x=1-20, y=1-42, cyclic, branched or straight-chain; alkyl halides, CxHyX z , x=1-20, y=0-42, z=1-42, X═F, Cl, Br, or I; any aromatic group (e.g., phenyl, alkylphenl, alkoxyphenyl, pyridine, naphthalene); cyclic complexes where at least one nitrogen is contained within the ring (e.g., 2-hexahydropyrimidin-2-ylidenehexahydropyrimidine, octahydropyrazino[2,3-b]pyrazine, pyrazino[2,3-b]pyrazine, quinoxalino[2,3-b]quinoxaline); any sulfur-containing group (e.g., sulfoxide, thiol, alkyl sulfide); any nitrogen-containing group (nitroxide, amine); any phosphorous containing group (phosphate); any boron-containing group (e.g., boronic acid); any organic acid (acetic acid, propanoic acid) and ester or amide derivatives thereof; any amino acid (e.g., glycine, cysteine, proline, glutamic acid, arginine, serine, histidine, 5-ammoniumvaleric acid) including alpha, beta, gamma, and greater derivatives; any silicon containing group (e.g., siloxane); and any alkoxy or group, —OCxHy, where x=0-20, y=1-42. 
     
       
         
         
             
             
         
       
     
     Formula 5 illustrates the structure of an ethene tetramine cation having the general formula of [(R 2 N) 2 C═C(NR 2 ) 2 ] +  as described above. Formula 6 illustrates examples of structures of several ethene tetramine ions that may serve as a cation “C” in a perovskite material. 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In certain embodiments, C may include an imidazolium cation, an aromatic, cyclic organic cation of the general formula [CRNRCRNRCR] +  where the R groups may be the same or different groups. Suitable R groups may include, but are not limited to: hydrogen, methyl, ethyl, propyl, butyl, pentyl group or isomer thereof; any alkane, alkene, or alkyne CxHy, where x=1-20, y=1-42, cyclic, branched or straight-chain; alkyl halides, CxHyXz, x=1-20, y=0-42, z=1-42, X═F, Cl, Br, or I; any aromatic group (e.g., phenyl, alkylphenl, alkoxyphenyl, pyridine, naphthalene); cyclic complexes where at least one nitrogen is contained within the ring (e.g., 2-hexahydropyrimidin-2-ylidenehexahydropyrimidine, octahydropyrazino[2,3-b]pyrazine, pyrazino[2,3-b]pyrazine, quinoxalino[2,3-b]quinoxaline); any sulfur-containing group (e.g., sulfoxide, thiol, alkyl sulfide); any nitrogen-containing group (nitroxide, amine); any phosphorous containing group (phosphate); any boron-containing group (e.g., boronic acid); any organic acid (acetic acid, propanoic acid) and ester or amide derivatives thereof; any amino acid (e.g., glycine, cysteine, proline, glutamic acid, arginine, serine, histidine, 5-ammoniumvaleric acid) including alpha, beta, gamma, and greater derivatives; any silicon containing group (e.g., siloxane); and any alkoxy or group, —OCxHy, where x=0-20, y=1-42. 
     
       
         
         
             
             
         
       
     
     In some embodiments, X may include one or more halides. In certain embodiments, X may instead or in addition include a Group 16 anion. In certain embodiments, the Group 16 anion may be oxide, sulfide, selenide, or telluride. In certain embodiments, X may instead or in addition include one or more a pseudohalides (e.g., cyanide, cyanate, isocyanate, fulminate, thiocyanate, isothiocyanate, azide, tetracarbonylcobaltate, carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide, and tricyanomethanide). 
     In one embodiment, a perovskite material may comprise the empirical formula CMX 3  where: C comprises one or more of the aforementioned cations, a Group 1 metal, a Group 2 metal, and/or other cations or cation-like compounds; M comprises one or more metals (examples including Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr); and X comprises one or more of the aforementioned anions. 
     In another embodiment, a perovskite material may comprise the empirical formula C′M 2 X 6  where: C′ comprises a cation with a 2+ charge including one or more of the aforementioned cations, diammonium butane, a Group 1 metal, a Group 2 metal, and/or other cations or cation-like compounds; M comprises one or more metals (examples including Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr); and X comprises one or more of the aforementioned anions. 
     In another embodiment, a perovskite material may comprise the empirical formula C′MX 4  where: C′ comprises a cation with a 2+ charge including one or more of the aforementioned cations, diammonium butane, a Group 1 metal, a Group 2 metal, and/or other cations or cation-like compounds; M comprises one or more metals (examples including Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr); and X comprises one or more of the aforementioned anions. In such an embodiment, the perovskite material may have a 2D structure. 
     In one embodiment, a perovskite material may comprise the empirical formula C 3 M 2 X 9  where: C comprises one or more of the aforementioned cations, a Group 1 metal, a Group 2 metal, and/or other cations or cation-like compounds; M comprises one or more metals (examples including Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr); and X comprises one or more of the aforementioned anions. 
     In one embodiment, a perovskite material may comprise the empirical formula CM2X7 where: C comprises one or more of the aforementioned cations, a Group 1 metal, a Group 2 metal, and/or other cations or cation-like compounds; M comprises one or more metals (examples including Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr n); and X comprises one or more of the aforementioned anions. 
     In one embodiment, a perovskite material may comprise the empirical formula C2MX4 where: C comprises one or more of the aforementioned cations, a Group 1 metal, a Group 2 metal, and/or other cations or cation-like compounds; M comprises one or more metals (examples including Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr); and X comprises one or more of the aforementioned anions. 
     Perovskite materials may also comprise mixed ion formulations where C, M, or X comprise two or more species, for example, Cs 0.1 FA 0.9 Pb(I 0.9 Cl 0.1 ) 3 ; Rb 0.1 FA 0.9 Pb(I 0.9 Cl 0.1 ) 3 Cs 0.1 FA 0.9 PbI 3 ; FAPb 0.5 Sn 0.5 I 3 ; FA 0.83 Cs 0.17 Pb(I 0.6 Br 0.4 ) 3 ; FA 0.83 Cs 0.12 Rb 0.05 Pb(I 0.6 Br 0.4 ) 3  and FA 0.85 MA 0.15 Pb(I 0.85 Br 0.15 ) 3 . 
     Composite Perovskite Material Device Design 
     In some embodiments, the present disclosure may provide composite design of PV and other similar devices (e.g., batteries, hybrid PV batteries, FETs, LEDs, nonlinear optics (NLOs), waveguides, etc.) including one or more perovskite materials. For example, one or more perovskite materials may serve as either or both of first and second active material of some embodiments (e.g., active materials  3906   a  and  3908   a  of  FIG.  3   ). In more general terms, some embodiments of the present disclosure provide PV or other devices having an active layer comprising one or more perovskite materials. In such embodiments, perovskite material (that is, material including any one or more perovskite materials(s)) may be employed in active layers of various architectures. Furthermore, perovskite material may serve the function(s) of any one or more components of an active layer (e.g., charge transport material, mesoporous material, photoactive material, and/or interfacial material, each of which is discussed in greater detail below). In some embodiments, the same perovskite materials may serve multiple such functions, although in other embodiments, a plurality of perovskite materials may be included in a device, each perovskite material serving one or more such functions. In certain embodiments, whatever role a perovskite material may serve, it may be prepared and/or present in a device in various states. For example, it may be substantially solid in some embodiments. A solution or suspension may be coated or otherwise deposited within a device (e.g., on another component of the device such as a mesoporous, interfacial, charge transport, photoactive, or other layer, and/or on an electrode). Perovskite materials in some embodiments may be formed in situ on a surface of another component of a device (e.g., by vapor deposition as a thin-film solid). Any other suitable means of forming a layer comprising perovskite material may be employed. 
     In general, a perovskite material device may include a first electrode, a second electrode, and an active layer comprising a perovskite material, the active layer disposed at least partially between the first and second electrodes. In some embodiments, the first electrode may be one of an anode and a cathode, and the second electrode may be the other of an anode and cathode. An active layer according to certain embodiments may include any one or more active layer components, including any one or more of: charge transport material; liquid electrolyte; mesoporous material; photoactive material (e.g., a dye, silicon, cadmium telluride, cadmium sulfide, cadmium selenide, copper indium gallium selenide, gallium arsenide, germanium indium phosphide, semiconducting polymers, other photoactive materials)); and interfacial material. Any one or more of these active layer components may include one or more perovskite materials. In some embodiments, some or all of the active layer components may be in whole or in part arranged in sub-layers. For example, the active layer may comprise any one or more of: an interfacial layer including interfacial material; a mesoporous layer including mesoporous material; and a charge transport layer including charge transport material. Further, an interfacial layer may be included between any two or more other layers of an active layer according to some embodiments and/or between an active layer component and an electrode. Reference to layers herein may include either a final arrangement (e.g., substantially discrete portions of each material separately definable within the device), and/or reference to a layer may mean arrangement during construction of a device, notwithstanding the possibility of subsequent intermixing of material(s) in each layer. Layers may in some embodiments be discrete and comprise substantially contiguous material (e.g., layers may be as stylistically illustrated in  FIG.  2   ). 
     In some embodiments, a perovskite material device may be a field effect transistor (FET). An FET perovskite material device may include a source electrode, drain electrode, gate electrode, dielectric layer, and a semiconductor layer. In some embodiments the semiconductor layer of an FET perovskite material device may be a perovskite material. 
     A perovskite material device according to some embodiments may optionally include one or more substrates. In some embodiments, either or both of the first and second electrode may be coated or otherwise disposed upon a substrate, such that the electrode is disposed substantially between a substrate and the active layer. The materials of composition of devices (e.g., substrate, electrode, active layer and/or active layer components) may in whole or in part be either rigid or flexible in various embodiments. In some embodiments, an electrode may act as a substrate, thereby negating the need for a separate substrate. 
     Furthermore, a perovskite material device according to certain embodiments may optionally include an anti-reflective layer or anti-reflective coating (ARC). In addition, a perovskite material device may include any one or more additives, such as any one or more of the additives discussed above with respect to some embodiments of the present disclosure. 
     Description of some of the various materials that may be included in a perovskite material device will be made in part with reference to  FIG.  2   .  FIG.  2    is a stylized diagram of a perovskite material device  3900  according to some embodiments. Although various components of the device  3900  are illustrated as discrete layers comprising contiguous material, it should be understood that  FIG.  2    is a stylized diagram; thus, embodiments in accordance with it may include such discrete layers, and/or substantially intermixed, non-contiguous layers, consistent with the usage of “layers” previously discussed herein. The device  3900  includes first and second substrates  3901  and  3913 . A first electrode  3902  is disposed upon an inner surface of the first substrate  3901 , and a second electrode  3912  is disposed on an inner surface of the second substrate  3913 . An active layer  3950  is sandwiched between the two electrodes  3902  and  3912 . The active layer  3950  includes a mesoporous layer  3904 ; first and second photoactive materials  3906  and  3908 ; a charge transport layer  3910 , and several interfacial layers.  FIG.  2    furthermore illustrates an example device  3900  according to embodiments wherein sub-layers of the active layer  3950  are separated by the interfacial layers, and further wherein interfacial layers are disposed upon each electrode  3902  and  3912 . In particular, second, third, and fourth interfacial layers  3905 ,  3907 , and  3909  are respectively disposed between each of the mesoporous layer  3904 , first photoactive material  3906 , second photoactive material  3908 , and charge transport layer  3910 . First and fifth interfacial layers  3903  and  3911  are respectively disposed between (i) the first electrode  3902  and mesoporous layer  3904 ; and (ii) the charge transport layer  3910  and second electrode  3912 . Thus, the architecture of the example device depicted in  FIG.  2    may be characterized as: substrate-electrode-active layer-electrode-substrate. The architecture of the active layer  3950  may be characterized as: interfacial layer-mesoporous layer-interfacial layer-photoactive material-interfacial layer-photoactive material-interfacial layer-charge transport layer-interfacial layer. As noted previously, in some embodiments, interfacial layers need not be present; or, one or more interfacial layers may be included only between certain, but not all, components of an active layer and/or components of a device. 
     A substrate, such as either or both of first and second substrates  3901  and  3913 , may be flexible or rigid. If two substrates are included, at least one should be transparent or translucent to electromagnetic (EM) radiation (such as, e.g., UV, visible, or IR radiation). If one substrate is included, it may be similarly transparent or translucent, although it need not be, so long as a portion of the device permits EM radiation to contact the active layer  3950 . Suitable substrate materials include any one or more of: glass; sapphire; magnesium oxide (MgO); mica; polymers (e.g., PEN, PET, PEG, polyolefin, polypropylene, polyethylene, polycarbonate, PMMA, polyamide, vinyl Kapton, etc.); ceramics; carbon; composites (e.g., fiberglass, Kevlar; carbon fiber); fabrics (e.g., cotton, nylon, silk, wool); wood; drywall; tiles (e.g. ceramic, composite, or clay); metal; steel; silver; gold; aluminum; magnesium; concrete; and combinations thereof. 
     As previously noted, an electrode (e.g., one of electrodes  3902  and  3912  of  FIG.  2   ) may be either an anode or a cathode. In some embodiments, one electrode may function as a cathode, and the other may function as an anode. Either or both electrodes  3902  and  3912  may be coupled to leads, cables, wires, or other means enabling charge transport to and/or from the device  3900 . An electrode may constitute any conductive material, and at least one electrode should be transparent or translucent to EM radiation, and/or be arranged in a manner that allows EM radiation to contact at least a portion of the active layer  3950 . Suitable electrode materials may include any one or more of: indium tin oxide or tin-doped indium oxide (ITO); fluorine-doped tin oxide (FTO); cadmium oxide (CdO); zinc indium tin oxide (ZITO); aluminum zinc oxide (AZO); aluminum (Al); gold (Au); silver (Ag); calcium (Ca); chromium (Cr); magnesium (Mg); titanium (Ti); steel; carbon (and allotropes thereof); doped carbon (e.g., nitrogen-doped); nanoparticles in core-shell configurations (e.g., silicon-carbon core-shell structure); and combinations thereof. 
     Mesoporous material (e.g., the material included in mesoporous layer  3904  of  FIG.  2   ) may include any pore-containing material. In some embodiments, the pores may have diameters ranging from about 1 to about 100 nm; in other embodiments, pore diameter may range from about 2 to about 50 nm. Suitable mesoporous material includes any one or more of: any interfacial material and/or mesoporous material discussed elsewhere herein; aluminum (Al); bismuth (Bi); cerium (Ce); hafnium (Hf); indium (In); molybdenum (Mo); niobium (Nb); nickel (Ni); silicon (Si); titanium (Ti); vanadium (V); zinc (Zn); zirconium (Zr); an oxide of any one or more of the foregoing metals (e.g., alumina, ceria, titania, zinc oxide, zirconia, etc.); a sulfide of any one or more of the foregoing metals; a nitride of any one or more of the foregoing metals; and combinations thereof. In some embodiments, any material disclosed herein as an IFL may be a mesoporous material. In other embodiments, the device illustrated by  FIG.  2    may not include a mesoporous material layer and include only thin-film, or “compact,” IFLs that are not mesoporous. 
     Photoactive material (e.g., first or second photoactive material  3906  or  3908  of  FIG.  2   ) may comprise any photoactive compound, such as any one or more of silicon (for example, polycrystalline silicon, single-crystalline silicon, or amorphous silicon), cadmium telluride, cadmium sulfide, cadmium selenide, copper indium gallium selenide, copper indium selenide, copper zinc tin sulfide, gallium arsenide, germanium, germanium indium phosphide, indium phosphide, one or more semiconducting polymers (e.g., polythiophenes (e.g., poly(3-hexylthiophene) and derivatives thereof, or P3HT); carbazole-based copolymers such as polyheptadecanylcarbazole dithienylbenzothiadiazole and derivatives thereof (e.g., PCDTBT); other copolymers such as polycyclopentadithiophene-benzothiadiazole and derivatives thereof (e.g., PCPDTBT), polybenzodithiophenyl-thienothiophenediyl and derivatives thereof (e.g., PTB6, PTB7, PTB7-th, PCE-10); poly(triaryl amine) compounds and derivatives thereof (e.g., PTAA); polyphenylene vinylenes and derivatives thereof (e.g., MDMO-PPV, MEH-PPV), and combinations thereof. 
     In certain embodiments, photoactive material may instead or in addition comprise a dye (e.g., N719, N 3 , other ruthenium-based dyes). In some embodiments, a dye (of whatever composition) may be coated onto another layer (e.g., a mesoporous layer and/or an interfacial layer). In some embodiments, photoactive material may include one or more perovskite materials. Perovskite-material-containing photoactive substance may be of a solid form, or in some embodiments it may take the form of a dye that includes a suspension or solution comprising perovskite material. Such a solution or suspension may be coated onto other device components in a manner similar to other dyes. In some embodiments, solid perovskite-containing material may be deposited by any suitable means (e.g., vapor deposition, solution deposition, direct placement of solid material, etc.). Devices according to various embodiments may include one, two, three, or more photoactive compounds (e.g., one, two, three, or more perovskite materials, dyes, or combinations thereof). In certain embodiments including multiple dyes or other photoactive materials, each of the two or more dyes or other photoactive materials may be separated by one or more interfacial layers. In some embodiments, multiple dyes and/or photoactive compounds may be at least in part intermixed. 
     Charge transport material (e.g., charge transport material of charge transport layer  3910  in  FIG.  2   ) may include solid-state charge transport material (i.e., a colloquially labeled solid-state electrolyte), or it may include a liquid electrolyte and/or ionic liquid. Any of the liquid electrolyte, ionic liquid, and solid-state charge transport material may be referred to as charge transport material. As used herein, “charge transport material” refers to any material, solid, liquid, or otherwise, capable of collecting charge carriers and/or transporting charge carriers. For instance, in PV devices according to some embodiments, a charge transport material may be capable of transporting charge carriers to an electrode. Charge carriers may include holes (the transport of which could make the charge transport material just as properly labeled “hole transport material”) and electrons. Holes may be transported toward an anode, and electrons toward a cathode, depending upon placement of the charge transport material in relation to either a cathode or anode in a PV or other device. Suitable examples of charge transport material according to some embodiments may include any one or more of: perovskite material; I − /I 3   − ; Co complexes; polythiophenes (e.g., poly(3-hexylthiophene) and derivatives thereof, or P3HT); carbazole-based copolymers such as polyheptadecanylcarbazole dithienylbenzothiadiazole and derivatives thereof (e.g., PCDTBT); other copolymers such as polycyclopentadithiophene-benzothiadiazole and derivatives thereof (e.g., PCPDTBT), polybenzodithiophenyl-thienothiophenediyl and derivatives thereof (e.g., PTB6, PTB7, PTB7-th, PCE-10); poly(triaryl amine) compounds and derivatives thereof (e.g., PTAA); Spiro-OMeTAD; polyphenylene vinylenes and derivatives thereof (e.g., MDMO-PPV, MEH-PPV); fullerenes and/or fullerene derivatives (e.g., C60, PCBM); carbon nanotubes; graphite; graphene; carbon black; amorphous carbon; glassy carbon; carbon fiber; and combinations thereof. In certain embodiments, charge transport material may include any material, solid or liquid, capable of collecting charge carriers (electrons or holes), and/or capable of transporting charge carriers. Charge transport material of some embodiments therefore may be n- or p-type active, ambipolar, and/or intrinsic semi-conducting material. Charge transport material may be disposed proximate to one of the electrodes of a device. It may in some embodiments be disposed adjacent to an electrode, although in other embodiments an interfacial layer may be disposed between the charge transport material and an electrode (as shown, e.g., in  FIG.  2    with the fifth interfacial layer  3911 ). In certain embodiments, the type of charge transport material may be selected based upon the electrode to which it is proximate. For example, if the charge transport material collects and/or transports holes, it may be proximate to an anode so as to transport holes to the anode. However, the charge transport material may instead be placed proximate to a cathode and be selected or constructed so as to transport electrons to the cathode. 
     As previously noted, devices according to various embodiments may optionally include an interfacial layer between any two other layers and/or materials, although devices according to some embodiments need not contain any interfacial layers. Thus, for example, a perovskite material device may contain zero, one, two, three, four, five, or more interfacial layers (such as the example device of  FIG.  2   , which contains five interfacial layers  3903 ,  3905 ,  3907 ,  3909 , and  3911 ). An interfacial layer may include a thin-coat interfacial layer in accordance with embodiments previously discussed herein (e.g., comprising alumina and/or other metal-oxide particles, and/or a titania/metal-oxide bilayer, and/or other compounds in accordance with thin-coat interfacial layers as discussed elsewhere herein). An interfacial layer according to some embodiments may include any suitable material for enhancing charge transport and/or collection between two layers or materials; it may also help prevent or reduce the likelihood of charge recombination once a charge has been transported away from one of the materials adjacent to the interfacial layer. Suitable interfacial materials may include any one or more of: any mesoporous material and/or interfacial material discussed elsewhere herein; Ag; Al; Au; B; Bi; Ca; Cd; Ce; Co; Cu; Fe; Ga; Ge; H; In; Mg; Mn; Mo; Nb; Ni; Pt; Sb; Sc; Si; Sn; Ta; Ti; V; W; Y; Zn; Zr; carbides of any of the foregoing metals (e.g., SiC, Fe 3 C; WC); silicides of any of the foregoing metals (e.g., Mg 2 Si, SrSi 2 , Sn 2 Si); oxides of any of the foregoing metals (e.g., alumina, silica, titania, SnO 2 , ZnO); sulfides of any of the foregoing metals (e.g., CdS, MoS 2 , SnS 2 ); nitrides of any of the foregoing metals (e.g., Mg 3 N 2 , TiN, BN, Si 3 N 4 ); selenides of any of the foregoing metals (e.g., CdSe, FeS 2 , ZnSe); tellurides of any of the foregoing metals (e.g., CdTe, TiTe 2 , ZnTe); phosphides of any of the foregoing metals (e.g., InP, GaP); arsenides of any of the foregoing metals (e.g., CoAs 3 , GaAs, InGaAs, NiAs); antimonides of any of the foregoing metals (e.g., AlSb, GaSb, InSb); halides of any of the foregoing metals (e.g., CuCl, CuI, BiI 3 ); pseudohalides of any of the foregoing metals (e.g., CuSCN, AuCN 2 ); carbonates of any of the foregoing metals (e.g., CaCO 3 , Ce 2 (CO 3 ) 3 ); functionalized or non-functionalized alkyl silyl groups; graphite; graphene; fullerenes; carbon nanotubes; any mesoporous material and/or interfacial material discussed elsewhere herein; and combinations thereof (including, in some embodiments, bilayers, trilayers, or multi-layers of combined materials). In some embodiments, an interfacial layer may include perovskite material. Further, interfacial layers may comprise doped embodiments of any interfacial material mentioned herein (e.g., Y-doped ZnO, N-doped single-wall carbon nanotubes). Interfacial layers may also comprise a compound having three of the above materials (e.g., CuTiO 3 , Zn 2 SnO 4 ) or a compound having four of the above materials (e.g., CoNiZnO). 
     As an example,  FIG.  3    illustrates an embodiment of a perovskite material device  3900   a  having a similar structure to perovskite material device  3900  illustrated by  FIG.  2   .  FIG.  3    is a stylized diagram of a perovskite material device  3900   a  according to some embodiments. Although various components of the device  3900   a  are illustrated as discrete layers comprising contiguous material, it should be understood that  FIG.  3    is a stylized diagram; thus, embodiments in accordance with it may include such discrete layers, and/or substantially intermixed, non-contiguous layers, consistent with the usage of “layers” previously discussed herein.  FIG.  3    includes an active layers  3906   a  and  3908   a.  One or both of active layers  3906   a  and  3908   a  may, in some embodiments, include any perovskite photoactive materials described above with respect to  FIG.  2   . In other embodiments, one or both of active layers  3906   a  and  3908   a  may include any photoactive material described herein, such as, thin film semiconductors (e.g., CdTe, CZTS, CIGS), photoactive polymers, dye sensitized photoactive materials, fullerenes, small molecule photoactive materials, and crystalline and polycrystalline semiconductor materials (e.g., silicon, GaAs, InP, Ge). In yet other embodiments, one or both of active layers  3906   a  and  3908   a  may include a light emitting diode (LED), field effect transistor (FET), thin film battery layer, or combinations thereof. In embodiments, one of active layers  3906   a  and  3908   a  may include a photoactive material and the other may include a light emitting diode (LED), field effect transistor (FET), thin film battery layer, or combinations thereof. For example, active layer  3908   a  may comprise a perovskite material photoactive layer and active layer  3906   b  may comprise a field effect transistor layer. Other layers illustrated of  FIG.  3   , such as layers  3901   a,    3902   a,    3903   a,    3904   a,    3905   a,    3907   a,    3909   a,    3910   a,    3911   a,    3912   a,  and 3913 a,  may be analogous to such corresponding layers as described herein with respect to  FIG.  2   . 
     Additionally, in some embodiments, a perovskite material may have three or more active layers. As an example,  FIG.  4    illustrates an embodiment of a perovskite material device  3900   b  having a similar structure to perovskite material device  3900  illustrated by  FIG.  2   .  FIG.  3    is a stylized diagram of a perovskite material device  3900   b  according to some embodiments. Although various components of the device  3900   b  are illustrated as discrete layers comprising contiguous material, it should be understood that  FIG.  4    is a stylized diagram; thus, embodiments in accordance with it may include such discrete layers, and/or substantially intermixed, non-contiguous layers, consistent with the usage of “layers” previously discussed herein.  FIG.  4    includes an active layers  3904   b,    3906   b  and  3908   b.  One or more of active layers  3904   b,    3906   b  and  3908   b  may, in some embodiments, include any perovskite photoactive materials described above with respect to  FIG.  2   . In other embodiments, one or more of active layers  3904   b,    3906   b  and 3908 b  may include any photoactive material described herein, such as, thin film semiconductors (e.g., CdTe, CZTS, CIGS), photoactive polymers, dye sensitized photoactive materials, fullerenes, small molecule photoactive materials, and crystalline and polycrystalline semiconductor materials (e.g., silicon, GaAs, InP, Ge). In yet other embodiments, one or more of active layers  3904   b,    3906   b  and  3908   b  may include a light emitting diode (LED), field effect transistor (FET), thin film battery layer, or combinations thereof. In embodiments, one or more of active layers of active layers  3904   b,    3906   b  and  3908   b  may include a photoactive material and the other may include a light emitting diode (LED), field effect transistor (FET), thin film battery layer, or combinations thereof. For example, active layer  3908   a  and  3906   b  may both comprise perovskite material photoactive layers and active layer  3904   b  may comprise a field effect transistor layer. Other layers illustrated of  FIG.  3   , such as layers  3901   b,    3902   b,    3903   b,    3904   b,    3905   b,    3907   b,    3909   b,    3910   b,    3911   b,    3912   b,  and  3913   b,  may be analogous to such corresponding layers as described herein with respect to  FIG.  2   . 
     Additional, more specific, example embodiments of perovskite devices will be discussed in terms of further stylized depictions of example devices. The stylized nature of these depictions,  FIGS.  1 - 4   , similarly is not intended to restrict the type of device which may in some embodiments be constructed in accordance with any one or more of  FIGS.  1 - 4   . That is, the architectures exhibited in  FIGS.  1 - 4    may be adapted so as to provide the BHJs, batteries, FETs, hybrid PV batteries, serial multi-cell PVs, parallel multi-cell PVs and other similar devices of other embodiments of the present disclosure, in accordance with any suitable means (including both those expressly discussed elsewhere herein, and other suitable means, which will be apparent to those skilled in the art with the benefit of this disclosure). 
     Formulation of the Perovskite Material Active Layer 
     As discussed earlier, in some embodiments, a perovskite material in the active layer may have the formulation CMX 3-y X′ y  (0≥y≥3), where: C comprises one or more cations (e.g., an amine, ammonium, a Group 1 metal, a Group 2 metal, formamidinium, guanidinium, ethene tetramine, phosphonium, imidazolium, and/or other cations or cation-like compounds); M comprises one or more metals (e.g., Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr); and X and X′ comprise one or more anions. In one embodiment, the perovskite material may comprise CPbI 3-y Cl y . In certain embodiments, the perovskite material may be deposited as an active layer in a PV device by, for example, drop casting, spin casting, slot-die printing, screen printing, or ink-jet printing onto a substrate layer using the steps described below. 
     First, a lead halide precursor ink is formed. An amount of lead halide may be massed in a clean, dry vessel in a controlled atmosphere environment (e.g., a controlled atmosphere box with glove-containing portholes allows for materials manipulation in an air-free environment). Suitable lead halides include, but are not limited to, lead (II) iodide, lead (II) bromide, lead (II) chloride, and lead (II) fluoride. The lead halide may comprise a single species of lead halide or it may comprise a lead halide mixture in a precise ratio. In certain embodiments, the lead halide mixture may comprise any binary, ternary, or quaternary ratio of 0.001-100 mol % of iodide, bromide, chloride, or fluoride. In one embodiment, the lead halide mixture may comprise lead (II) chloride and lead (II) iodide in a ratio of about 10:90 mol:mol. In other embodiments, the lead halide mixture may comprise lead (II) chloride and lead (II) iodide in a ratio of about 5:95, about 7.5:92.5, or about 15:85 mol:mol. 
     Alternatively, other lead salt precursors may be used in conjunction with or in lieu of lead halide salts to form the precursor ink. Suitable precursor salts may comprise any combination of lead (II) or lead(IV) and the following anions: nitrate, nitrite, carboxylate, acetate, acetonyl acetonate, formate, oxalate, sulfate, sulfite, thiosulfate, phosphate, tetrafluoroborate, hexafluorophosphate, tetra(perfluorophenyl) borate, hydride, oxide, peroxide, hydroxide, nitride, arsenate, arsenite, perchlorate, carbonate, bicarbonate, chromate, dichromate, iodate, bromate, chlorate, chlorite, hypochlorite, hypobromite, cyanide, cyanate, isocyanate, fulminate, thiocyanate, isothiocyanate, azide, tetracarbonylcobaltate, carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide, tricyanomethanide, amide, and permanganate. 
     The precursor ink may further comprise a lead (II) or lead (IV) salt in mole ratios of 0 to 100% to the following metal ions Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr as a salt of the aforementioned anions. 
     A solvent may then be added to the vessel to dissolve the lead solids to form the lead halide precursor ink. Suitable solvents include, but are not limited to, dry N-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone, dimethylformamide, dialkylformamide, dimethylsulfoxide (DMSO), methanol, ethanol, propanol, butanol, tetrahydrofuran, formamide, tert-butylpyridine, pyridine, alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, and combinations thereof. In one embodiment, the lead solids are dissolved in dry dimethylformamide (DMF). The lead solids may be dissolved at a temperature between about 20° C. to about 150° C. In one embodiment, the lead solids are dissolved at about 85° C. The lead solids may be dissolved for as long as necessary to form a solution, which may take place over a time period up to about 72 hours. The resulting solution forms the base of the lead halide precursor ink. In some embodiments, the lead halide precursor ink may have a lead halide concentration between about 0.001M and about 10M. In one embodiment, the lead halide precursor ink has a lead halide concentration of about 1 M. 
     Optionally, certain additives may be added to the lead halide precursor ink to affect the final perovskite crystallinity and stability. In some embodiments, the lead halide precursor ink may further comprise an amino acid (e.g., 5-aminovaleric acid, histidine, glycine, lysine), an amino acid hydrohalide (e.g., 5-amino valeric acid hydrochloride), an IFL surface-modifying (SAM) agent (such as those discussed earlier in the specification), or a combination thereof. In one embodiment, formamidinium chloride may be added to the lead halide precursor ink. In other embodiments, the halide of any cation discussed earlier in the specification may be used. In some embodiments, combinations of additives may be added to the lead halide precursor ink including, for example, the combination of formamidinium chloride and 5-amino valeric acid hydrochloride. 
     By way of explanation, and without limiting the disclosure to any particular theory of mechanism, it has been found that formamidinium chloride and 5-amino valeric acid improve perovskite PV device stability when they are used as additives or counter-cations in a one-step perovskite device fabrication. It has also been found that chloride, in the form of PbCl 2 , improves perovskite PV device performance when added to a PbI 2  precursor solution in a two-step method. It has been found that the two-step perovskite thin film deposition process may be improved by adding formamidinium chloride and/or 5-amino valeric acid hydrochloride directly to a lead halide precursor solution (e.g., PbI 2 ) to leverage both advantages with a single material. Other perovskite film deposition processes may likewise be improved by the addition of formamidinium chloride, 5-amino valeric acid hydrochloride, or PbCl 2  to a lead halide precursor solution. 
     The additives, including formamidinium chloride and/or 5-amino valeric acid hydrochloride. may be added to the lead halide precursor ink at various concentrations depending on the desired characteristics of the resulting perovskite material. In one embodiment, the additives may be added in a concentration of about 1 nM to about 1 M. In another embodiment, the additives may be added in a concentration of about 1 μM to about 1 M. In another embodiment, the additives may be added in a concentration of about 1 μM to about 1 mM. 
     Optionally, in certain embodiments, water may be added to the lead halide precursor ink. By way of explanation, and without limiting the disclosure to any particular theory or mechanism, the presence of water affects perovskite thin-film crystalline growth. Under normal circumstances, water may be absorbed as vapor from the air. However, it is possible to control the perovskite PV crystallinity through the direct addition of water to the lead halide precursor ink in specific concentrations. Suitable water includes distilled, deionized water, or any other source of water that is substantially free of contaminants (including minerals). It has been found, based on light I-V sweeps, that the perovskite PV light-to-power conversion efficiency may nearly triple with the addition of water compared to a completely dry device. 
     The water may be added to the lead halide precursor ink at various concentrations depending on the desired characteristics of the resulting perovskite material. In one embodiment, the water may be added in a concentration of about 1 nL/mL to about 1 mL/mL. In another embodiment, the water may be added in a concentration of about 1 μL/mL to about 0.1 mL/mL. In another embodiment, the water may be added in a concentration of about 1 μL/mL to about 20 μL/mL. 
     The lead halide precursor ink may then be deposited on the desired substrate. Suitable substrate layers may include any of the substrate layers identified earlier in this disclosure. As noted above, the lead halide precursor ink may be deposited through a variety of means, including but not limited to, drop casting, spin casting, slot-die printing, screen printing, or ink-jet printing. In certain embodiments, the lead halide precursor ink may be spin-coated onto the substrate at a speed of about 500 rpm to about 10,000 rpm for a time period of about 5 seconds to about 600 seconds. In one embodiment, the lead halide precursor ink may be spin-coated onto the substrate at about 3000 rpm for about 30 seconds. The lead halide precursor ink may be deposited on the substrate at an ambient atmosphere in a humidity range of about 0% relative humidity to about 50% relative humidity. The lead halide precursor ink may then be allowed to dry in a substantially water-free atmosphere, i.e., less than 30% relative humidity, to form a thin film. 
     The thin film may then be thermally annealed for a time period up to about 24 hours at a temperature of about 20° C. to about 300° C. In one embodiment, the thin film may be thermally annealed for about ten minutes at a temperature of about 50° C. The perovskite material active layer may then be completed by a conversion process in which the precursor film is submerged or rinsed with a solution comprising a solvent or mixture of solvents (e.g., DMF, isopropanol, methanol, ethanol, butanol, chloroform chlorobenzene, dimethylsulfoxide, water) and salt (e.g., methylammonium iodide, formamidinium iodide, guanidinium iodide, 1,2,2-triaminovinylammonium iodide, 5-aminovaleric acid hydroiodide) in a concentration between 0.001M and 10M. In certain embodiments, the thin films may also be thermally post-annealed in the same fashion as in the first line of this paragraph. 
     In some embodiments, a lead salt precursor may be deposited onto a substrate to form a lead salt thin film. The substrate may have a temperature about equal to ambient temperature or have a controlled temperature between 0° C. and 500° C. The lead salt precursor may be deposited by a variety of methods known in the art, including but not limited to spin-coating, slot-die printing, ink-jet printing, gravure printing, screen printing, sputtering, PE-CVD, thermal evaporation, or spray coating. Deposition of the lead salt precursor may be performed in a variety of atmospheres at ambient pressure (e.g. about one atmosphere, depending on elevation and atmospheric conditions) or at pressures less than atmospheric or ambient (e.g., 1 mTorr to 500 mTorr). The deposition atmosphere may comprise ambient air, a controlled humidity environment (e.g., 0-100 g H 2 O/m 3  of gas), pure argon, pure nitrogen, pure oxygen, pure hydrogen, pure helium, pure neon, pure krypton, pure CO 2  or any combination of the preceding gases. A controlled humidity environment may include an environment in which the absolute humidity or the % relative humidity is held at a fixed value, or in which the absolute humidity or the % relative humidity varies according to predetermined set points or a predetermined function. In particular embodiments, deposition may occur in a controlled humidity environment having a % relative humidity greater than or equal to 0% and less than or equal to 50%. In other embodiments, deposition may occur in a controlled humidity environment containing greater than or equal to 0 g H 2 O/m 3  gas and less than or equal to 20 g H 2 O/m 3  gas. 
     The lead salt precursor may be a liquid, a gas, solid, or combination of these states of matter such as a solution, suspension, colloid, foam, gel, or aerosol. In some embodiments, the lead salt precursor may be a solution containing one or more solvents. For example, the lead salt precursor may contain one or more of N-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone, dimethylformamide, dialkylformamide, dimethylsulfoxide (DMSO), methanol, ethanol, propanol, butanol, tetrahydrofuran, formamide, tert-butylpyridine, pyridine, alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, and combinations thereof. The lead salt precursor may comprise a single lead salt (e.g., lead (II) iodide, lead (II) thiocyanate) or any combination of those disclosed herein (e.g., PbI 2 +PbCl 2 ; PbI 2 +Pb(SCN) 2 ). The lead salt precursor may also contain one or more additives such as an amino acid (e.g., 5-aminovaleric acid hydroiodide), 1,8-diiodooctane, 1,8-dithiooctane, formamidinium halide, acetic acid, trifluoroacetic acid, a methylammonium halide, or water. The lead halide precursor ink may be allowed to dry in a substantially water-free atmosphere, i.e., less than 30% relative humidity, to form a thin film. The thin film may then be thermally annealed for a time period of up to about 24 hours at a temperature of about 20° C. to about 300° C. Annealing may be performed in a variety of atmospheres at ambient pressure (e.g. about one atmosphere, depending on elevation and atmospheric conditions) or at pressures less than atmospheric or ambient (e.g., 1 mTorr to 500 mTorr). An annealing atmosphere may comprise ambient air, a controlled humidity environment (e.g., 0-100 g H 2 O/m 3  of gas), pure argon, pure nitrogen, pure oxygen, pure hydrogen, pure helium, pure neon, pure krypton, pure CO 2  or any combination of the preceding gases. A controlled humidity environment may include an environment in which the absolute humidity or the % relative humidity is held at a fixed value, or in which the absolute humidity or the % relative humidity varies according to predetermined set points or a predetermined function. In particular embodiments, annealing may occur in a controlled humidity environment having a % relative humidity greater than or equal to 0% and less than or equal to 50%. In other embodiments, annealing may occur in a controlled humidity environment containing greater than or equal to 0 g H 2 O/m 3  gas and less than or equal to 20 g H 2 O/m 3  gas 
     After the lead salt precursor is deposited, a second salt precursor (e.g., formamidinium iodide, formamidinium thiocyanate, or guanidinium thiocyanate) may be deposited onto the lead salt thin film, where the lead salt thin film may have a temperature about equal to ambient temperature or have a controlled temperature between 0° C. and 500° C. The second salt precursor, in some embodiments, may be deposited at ambient temperature or at elevated temperature between about 25° C. and 125° C. The second salt precursor may be deposited by a variety of methods known in the art, including but not limited to spin-coating, slot-die printing, ink-jet printing, gravure printing, screen printing, sputtering, PE-CVD, thermal evaporation, or spray coating. Deposition of the second salt precursor may be performed in a variety of atmospheres at ambient pressure (e.g. about one atmosphere, depending on elevation and atmospheric conditions) or at pressures less than atmospheric or ambient (e.g., 1 mTorr to 500 mTorr). The deposition atmosphere may comprise ambient air, a controlled humidity environment (e.g., 0-100 g H 2 O/m 3  of gas), pure argon, pure nitrogen, pure oxygen, pure hydrogen, pure helium, pure neon, pure krypton, pure CO 2  or any combination of the preceding gases. A controlled humidity environment may include an environment in which the absolute humidity or the % relative humidity is held at a fixed value, or in which the absolute humidity or the % relative humidity varies according to predetermined set points or a predetermined function. In particular embodiments, deposition may occur in a controlled humidity environment having a % relative humidity greater than or equal to 0% and less than or equal to 50%. In other embodiments, deposition may occur in a controlled humidity environment containing greater than or equal to 0 g H 2 O/m 3  gas and less than or equal to 20 g H 2 O/m 3  gas. 
     In some embodiments the second salt precursor may be a solution containing one or more solvents. For example, the second salt precursor may contain one or more of dry N-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone, dimethylformamide, dialkylformamide, dimethylsulfoxide (DMSO), methanol, ethanol, propanol, butanol, tetrahydrofuran, formamide, tert-butylpyridine, pyridine, alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, and combinations thereof. 
     After deposition of the lead salt precursor and second salt precursor, the substrate may be annealed. Annealing the substrate may convert the lead salt precursor and second salt precursor to a perovskite material, (e.g. FAPbI 3 , GAPb(SCN) 3 , FASnI 3 ). Annealing may be performed in a variety of atmospheres at ambient pressure (e.g. about one atmosphere, depending on elevation and atmospheric conditions) or at pressures less than atmospheric or ambient (e.g., 1 mTorr to 500 mTorr). An annealing atmosphere may comprise ambient air, a controlled humidity environment (e.g., 0-100 g H 2 O/m 3  of gas), pure argon, pure nitrogen, pure oxygen, pure hydrogen, pure helium, pure neon, pure krypton, pure CO 2  or any combination of the preceding gases. A controlled humidity environment may include an environment in which the absolute humidity or the % relative humidity is held at a fixed value, or in which the absolute humidity or the % relative humidity varies according to predetermined set points or a predetermined function. In particular embodiments, annealing may occur in a controlled humidity environment having a % relative humidity greater than or equal to 0% and less than or equal to 50%. In other embodiments, annealing may occur in a controlled humidity environment containing greater than or equal to 0 g H 2 O/m 3  gas and less than or equal to 20 g H 2 O/m 3  gas. In some embodiments, annealing may occur at a temperature greater than or equal to 50° C. and less than or equal to 300° C. Unless described as otherwise, any annealing or deposition step described herein may be carried out under the preceding conditions. 
     For example, in a particular embodiment, a FAPbI 3  perovskite material may be formed by the following process. First a lead (II) halide precursor comprising about a 90:10 mole ratio of PbI 2  to PbCl 2  dissolved in anhydrous DMF may be deposited onto a substrate by spin-coating or slot-die printing. The lead halide precursor ink may be allowed to dry in a substantially water-free atmosphere, i.e., less than 30% relative humidity, for approximately one hour (+15 minutes) to form a thin film. The thin film may be subsequently thermally annealed for about ten minutes at a temperature of about 50° C. (±10° C.). In other embodiments, the lead halide precursor may be deposited by ink-jet printing, gravure printing, screen printing, sputtering, PE-CVD, atomic-layer deposition, thermal evaporation, or spray coating. Next, a formamidinium iodide precursor comprising a 25-60 mg/mL concentration of formamidinium iodide dissolved in anhydrous isopropyl alcohol may be deposited onto the lead halide thin film by spin coating or slot-die printing. In other embodiments, the formamidinium iodide precursor may be deposited by ink-jet printing, gravure printing, screen printing, sputtering, PE-CVD, atomic-layer deposition, thermal evaporation, or spray coating. After depositing the lead halide precursor and formamidinium iodide precursor, the substrate may be annealed at about 25% relative humidity (about 4 to 7 g H 2 O/m 3  air) and between about 125° C. and 200° C. to form a formamidinium lead iodide (FAPbI 3 ) perovskite material. 
     In another embodiment, a perovskite material may comprise C′CPbX 3 , where C′ is one or more Group 1 metals (i.e. Li, Na, K, Rb, Cs). In a particular embodiment M′ may be cesium (Cs). In another embodiment C′ may be rubidium (Rb). In another embodiment C′ may be sodium (Na). In another embodiment C′ may be potassium (K). In yet other embodiments, a perovskite material may comprise C′ v C w Pb y X z , where C′ is one or more Group 1 metals and v, w, y, and z represent real numbers between 1 and 20. In certain embodiments, the perovskite material may be deposited as an active layer in a PV device by, for example, drop casting, spin casting, gravure coating, blade coating, reverse gravure coating, slot-die printing, screen printing, or ink-jet printing onto a substrate layer using the steps described below. 
     First, a lead halide solution is formed. An amount of lead halide may be massed in a clean, dry vessel in a controlled atmosphere environment. Suitable lead halides include, but are not limited to, lead (II) iodide, lead (II) bromide, lead (II) chloride, and lead (II) fluoride. The lead halide may comprise a single species of lead halide or it may comprise a lead halide mixture in a precise ratio. In one embodiment the lead halide may comprise lead (II) iodide. In certain embodiments, the lead halide mixture may comprise any binary, ternary, or quaternary ratio of 0.001-100 mol % of iodide, bromide, chloride, or fluoride. In one embodiment, the lead halide mixture may comprise lead (II) chloride and lead (II) iodide in a ratio of about 10:90 mol:mol. In other embodiments, the lead halide mixture may comprise lead (II) chloride and lead (II) iodide in a ratio of about 5:95, about 7.5:92.5, or about 15:85 mol:mol. 
     Alternatively, other lead salt precursors may be used in conjunction with or in lieu of lead halide salts to form a lead salt solution. Suitable precursor lead salts may comprise any combination of lead (II) or lead(IV) and the following anions: nitrate, nitrite, carboxylate, acetate, formate, oxalate, sulfate, sulfite, thiosulfate, phosphate, tetrafluoroborate, hexafluorophosphate, tetra(perfluorophenyl) borate, hydride, oxide, peroxide, hydroxide, nitride, arsenate, arsenite, perchlorate, carbonate, bicarbonate, chromate, dichromate, iodate, bromate, chlorate, chlorite, hypochlorite, hypobromite, cyanide, cyanate, isocyanate, fulminate, thiocyanate, isothiocyanate, azide, tetracarbonylcobaltate, carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide, tricyanomethanide, amide, and permanganate. 
     The lead salt solution may further comprise a lead (II) or lead (IV) salt in mole ratios of 0 to 100% to the following metal ions Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, Pb, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr as a salt of the aforementioned anions. 
     A solvent may then be added to the vessel to dissolve the lead halide solids to form the lead halide solution. Suitable solvents include, but are not limited to, dry N-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone, dimethylformamide (DMF), dialkylformamide, dimethylsulfoxide (DMSO), methanol, ethanol, propanol, butanol, tetrahydrofuran, formamide, tert-butylpyridine, pyridine, alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, and combinations thereof. In one embodiment, the lead solids are dissolved in dry dimethylformamide (DMF). The lead halide solids may be dissolved at a temperature between about 20° C. to about 150° C. In one embodiment, the lead halide solids are dissolved at about 85° C. The lead halide solids may be dissolved for as long as necessary to form a solution, which may take place over a time period up to about 72 hours. The resulting solution forms the base of the lead halide precursor ink. In some embodiments, the lead halide precursor ink may have a lead halide concentration between about 0.001M and about 10M. In one embodiment, the lead halide precursor ink has a lead halide concentration of about 1 M. In some embodiments, the lead halide solution may further comprise an amino acid (e.g., 5-aminovaleric acid, histidine, glycine, lysine), an amino acid hydrohalide (e.g., 5-amino valeric acid hydrochloride), an IFL surface-modifying (SAM) agent (such as those discussed earlier in the specification), or a combination thereof. 
     Next, a Group 1 metal halide solution is formed. An amount of Group 1 metal halide may be massed in a clean, dry vessel in a controlled atmosphere environment. Suitable Group 1 metal halides include, but are not limited to, cesium iodide, cesium bromide, cesium chloride, cesium fluoride, rubidium iodide, rubidium bromide, rubidium chloride, rubidium fluoride, lithium iodide, lithium bromide, lithium chloride, lithium fluoride, sodium iodide, sodium bromide, sodium chloride, sodium fluoride, potassium iodide, potassium bromide, potassium chloride, potassium fluoride. The Group 1 metal halide may comprise a single species of Group 1 metal halide or it may comprise a Group 1 metal halide mixture in a precise ratio. In one embodiment the Group 1 metal halide may comprise cesium iodide. In another embodiment the Group 1 metal halide may comprise rubidium iodide. In another embodiment the Group 1 metal halide may comprise sodium iodide. In another embodiment the Group 1 metal halide may comprise potassium iodide. 
     Alternatively, other Group 1 metal salt precursors may be used in conjunction with or in lieu of Group 1 metal halide salts to form a Group 1 metal salt solution. Suitable precursor Group 1 metal salts may comprise any combination of Group 1 metals and the following anions: nitrate, nitrite, carboxylate, acetate, formate, oxalate, sulfate, sulfite, thiosulfate, phosphate, tetrafluoroborate, hexafluorophosphate, tetra(perfluorophenyl) borate, hydride, oxide, peroxide, hydroxide, nitride, arsenate, arsenite, perchlorate, carbonate, bicarbonate, chromate, dichromate, iodate, bromate, chlorate, chlorite, hypochlorite, hypobromite, cyanide, cyanate, isocyanate, fulminate, thiocyanate, isothiocyanate, azide, tetracarbonylcobaltate, carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide, tricyanomethanide, amide, and permanganate. 
     A solvent may then be added to the vessel to dissolve the Group 1 metal halide solids to form the Group 1 metal halide solution. Suitable solvents include, but are not limited to, dry N-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone, dimethylformamide (DMF), dialkylformamide, dimethylsulfoxide (DMSO), methanol, ethanol, propanol, butanol, tetrahydrofuran, formamide, tert-butylpyridine, pyridine, alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, and combinations thereof. In one embodiment, the lead solids are dissolved in dry dimethylsulfoxide (DMSO). The Group 1 metal halide solids may be dissolved at a temperature between about 20° C. to about 150° C. In one embodiment, the Group 1 metal halide solids are dissolved at room temperature (i.e. about 25° C.). The Group 1 metal halide solids may be dissolved for as long as necessary to form a solution, which may take place over a time period up to about 72 hours. The resulting solution forms the Group 1 metal halide solution. In some embodiments, the Group 1 metal halide solution may have a Group 1 metal halide concentration between about 0.001M and about 10M. In one embodiment, the Group 1 metal halide solution has a Group 1 metal halide concentration of about 1 M. In some embodiments, the Group 1 metal halide solution may further comprise an amino acid (e.g., 5-aminovaleric acid, histidine, glycine, lysine), an amino acid hydrohalide (e.g., 5-amino valeric acid hydrochloride), an IFL surface-modifying (SAM) agent (such as those discussed earlier in the specification), or a combination thereof. 
     Next, the lead halide solution and the Group 1 metal halide solution are mixed to form a thin-film precursor ink. The lead halide solution and Group 1 metal halide solution may be mixed in a ratio such that the resulting thin-film precursor ink has a molar concentration of the Group 1 metal halide that is between 0% and 25% of the molar concentration of the lead halide. In particular embodiments, the thin-film precursor ink may have a molar concentration of the Group 1 metal halide that is 1% of the molar concentration of the lead halide. In particular embodiments, the thin-film precursor ink may have a molar concentration of the Group 1 metal halide that is 5% of the molar concentration of the lead halide. In particular embodiments, the thin-film precursor ink may have a molar concentration of the Group 1 metal halide that is 10% of the molar concentration of the lead halide. In particular embodiments, the thin-film precursor ink may have a molar concentration of the Group 1 metal halide that is 15% of the molar concentration of the lead halide. In particular embodiments, the thin-film precursor ink may have a molar concentration of the Group 1 metal halide that is 20% of the molar concentration of the lead halide. In particular embodiments, the thin-film precursor ink may have a molar concentration of the Group 1 metal halide that is 25% of the molar concentration of the lead halide. In some embodiments the lead halide solution and the Group 1 metal halide solution may be stirred or agitated during or after mixing, 
     The thin-film precursor ink may then be deposited on the desired substrate. Suitable substrate layers may include any of the substrate layers identified earlier in this disclosure. As noted above, the thin-film precursor ink may be deposited through a variety of means, including but not limited to, drop casting, spin casting, gravure coating, blade coating, reverse gravure coating, slot-die printing, screen printing, or ink-jet printing. In certain embodiments, the thin-film precursor ink may be spin-coated onto the substrate at a speed of about 500 rpm to about 10,000 rpm for a time period of about 5 seconds to about 600 seconds. In one embodiment, the thin-film precursor ink may be spin-coated onto the substrate at about 3000 rpm for about 30 seconds. The thin-film precursor ink may be deposited on the substrate at an ambient atmosphere in a humidity range of about 0% relative humidity to about 50% relative humidity. The thin-film precursor ink may then be allowed to dry in a substantially water-free atmosphere, i.e., less than 30% relative humidity or 7 g H 2 O/m 3 , to form a thin film. 
     The thin film can then be thermally annealed for a time period up to about 24 hours at a temperature of about 20° C. to about 300° C. In one embodiment, the thin film may be thermally annealed for about ten minutes at a temperature of about 50° C. The perovskite material active layer may then be completed by a conversion process in which the precursor film is submerged or rinsed with a salt solution comprising a solvent or mixture of solvents (e.g., DMF, isopropanol, methanol, ethanol, butanol, chloroform chlorobenzene, dimethylsulfoxide, water) and salt (e.g., methylammonium iodide, formamidinium iodide, guanidinium iodide, 1,2,2-triaminovinylammonium iodide, 5-aminovaleric acid hydroiodide) in a concentration between 0.001M and 10M. In certain embodiments, the perovskite material thin films can also be thermally post-annealed in the same fashion as in the first line of this paragraph. 
     In some embodiments, the salt solution may be prepared by massing the salt in a clean, dry vessel in a controlled atmosphere environment. Suitable salts include, but are not limited to, methylammonium iodide, formamidinium iodide, guanidinium iodide, imidazolium iodide, ethene tetramine iodide, 1,2,2-triaminovinylammonium iodide, and 5-aminovaleric acid hydroiodide. Other suitable salts may include any organic cation described above in the section entitled “Perovskite Material.” The salt may comprise a single species of salt or it may comprise a salt mixture in a precise ratio. In one embodiment the salt may comprise methylammonium iodide. In another embodiment the salt may comprise formamidinium iodide. Next, a solvent may then be added to the vessel to dissolve the salt solids to form the salt solution. Suitable solvents include, but are not limited to, DMF, isopropanol, methanol, ethanol, butanol, chloroform chlorobenzene, dimethylsulfoxide, water, and combinations thereof. In one embodiment, formamidinium iodide salt solids are dissolved in isopropanol. The salt solids may be dissolved at a temperature between about 20° C. to about 150° C. In one embodiment, the salt solids are dissolved at room temperature (i.e. about 25° C.). The salt solids may be dissolved for as long as necessary to form a solution, which may take place over a time period up to about 72 hours. The resulting solution forms the salt solution. In some embodiments, the salt solution may have a salt concentration between about 0.001M and about 10M. In one embodiment, the salt solution has a salt concentration of about 1 M. 
     For example, using the process described above with a lead (II) iodide solution, a cesium iodide solution, and a methylammonium (MA) iodide salt solution may result in a perovskite material having the a formula of Cs i MAPbI 3 , where i equals a number between 0 and 1. As another example, using a lead (II) iodide solution, a rubidium iodide solution, and a formamidinium (FA) iodide salt solution may result in a perovskite material having the a formula of Rb i FAPbI 3 , where i equals a number between 0 and 1. As another example, the using a lead (II) iodide solution, a cesium iodide solution, and a formamidinium (FA) iodide salt solution may result in a perovskite material having the a formula of Cs i FAPbI 3 , where i equals a number between 0 and 1. As another example, the using a lead (II) iodide solution, a potassium iodide solution, and a formamidinium (FA) iodide salt solution may result in a perovskite material having the a formula of K i FAPbI 3 , where i equals a number between 0 and 1. As another example, the using a lead (II) iodide solution, a sodium iodide solution, and a formamidinium (FA) iodide salt solution may result in a perovskite material having the a formula of Na i FAPbI 3 , where i equals a number between 0 and 1. As another example, the using a lead (II) iodide-lead (II) chloride mixture solution, a cesium iodide solution, and a formamidinium (FA) iodide salt solution may result in a perovskite material having the a formula of Cs i FAPbI 3-y Cl y , where i equals a number between 0 and 1 and y represents a number between 0 and 3. 
     In a particular embodiment, the lead halide solution as described above may have a ratio of 90:10 of PbI 2  to PbCl 2  on a mole basis. A cesium iodide (CsI) solution may be added to the lead halide solution by the method described above to form a thin film precursor ink with 10 mol % CsI. A FAPbI 3  perovskite material may be produced according to the method described above using this thin film precursor solution. The addition of cesium ions through the CsI solution as described above may cause chloride anions and Cesium atoms to incorporate into the FAPbI 3  crystal lattice. This may result in a greater degree of lattice contraction compared to addition of cesium or rubidium ions as described above without addition of chloride ions. Table 1 below shows lattice parameters for FAPbI 3  perovskite materials with 10 mol % rubidium and 20 mol % chloride (e.g. 10 mol % PbCl 2 ), 10 mol % cesium, and 10 mol % cesium with 20 mol % chloride, wherein the mol % concentration represents the concentration of the additive with respect to the lead atoms in the lead halide solution. As can be seen in Table 1, the FAPbI 3  perovskite material with cesium and chloride added has smaller lattice parameters than the other two perovskite material samples. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 (001) 
                 (002) 
               
               
                 Sample Details 
                 d-spacing 
                 d-spacing 
               
               
                   
               
             
            
               
                 10 mol % Rbl + 
                 6.3759(15) 
                 3.1822(5) 
               
               
                 10 mol % PbCl 2   
                   
                   
               
               
                 10 mol % Csl + 
                 6.3425(13) 
                 3.1736(8) 
               
               
                 0 mol % PbCl 2   
                   
                   
               
               
                 10 mol % Csl + 
                 6.3272(13) 
                 3.1633(4) 
               
               
                 10 mol % PbCl 2   
               
               
                   
               
            
           
         
       
     
     Additionally, data shows that the FAPbI 3  perovskite material with rubidium, cesium and/or chloride added has a Pm3-m cubic structure. FAPbI 3  perovskites with up to and including 10 mol % Rb and 10 mol % Cl, or 10 mol % Cs, or 10 mol % Cs and 10 mol % Cl have been observed to maintain a cubic Pm3-m cubic crystal structure.  FIG.  29    shows x-ray diffraction patterns corresponding to each of the samples presented in Table 1. Tables 2-4 provide the x-ray diffraction peaks and intensity for the three perovskite materials shown in Table 1. The data were collected at ambient conditions on a Rigaku Miniflex 600 using a Cu Kα radiation source at a scan rate of 1.5 degrees 2θ/min. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 10 mol % Rbl + 10 mol % PbCl2 
               
            
           
           
               
               
               
               
               
            
               
                   
                 2-theta 
                 d 
                 Height 
                 Peak Identity 
               
               
                   
                 (deg) 
                 (ang.) 
                 (cps) 
                 (phase, miller index) 
               
               
                   
                   
               
               
                   
                   
                   
                   
                 Pbl2, (001) 
               
               
                   
                 13.878(3) 
                 6.3759(15) 
                 12605(126) 
                 Perovskite, (001) 
               
               
                   
                 19.707(15) 
                  4.501(3) 
                  489(25) 
                 Perovskite, (011) 
               
               
                   
                 21.320(14) 
                  4.164(3) 
                  286(19) 
                 ITO, (112) 
               
               
                   
                 24.227(19) 
                  3.671(3) 
                  1022(36) 
                 Perovskite, (111) 
               
               
                   
                 28.017(4) 
                 3.1822(5) 
                  5683(84) 
                 Perovskite, (002) 
               
               
                   
                  30.13(4) 
                  2.964(4) 
                  344(21) 
                 ITO, (112) 
               
               
                   
                 31.403(14) 
                 2.8464(13) 
                  913(34) 
                 Perovskite, (012) 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 10 mol % Csl &amp; 0 mol % PbCl2 
               
            
           
           
               
               
               
               
               
            
               
                   
                 2-theta 
                 d 
                 Height 
                 Peak Identity 
               
               
                   
                 (deg) 
                 (ang.) 
                 (cps) 
                 phase (miller index) 
               
               
                   
                   
               
               
                   
                 12.614(14) 
                  7.012(8) 
                  99(11) 
                 Pbl2, (001) 
               
               
                   
                 13.952(3) 
                 6.3425(13) 
                 4921(78) 
                 Perovskite, (001) 
               
               
                   
                 19.826(12) 
                  4.475(3) 
                  392(22) 
                 Perovskite, (011) 
               
               
                   
                 21.274(14) 
                  4.173(3) 
                  281(19) 
                 ITO, (112) 
               
               
                   
                 24.333(15) 
                  3.655(2) 
                 1031(36) 
                 Perovskite, (111) 
               
               
                   
                 28.094(7) 
                 3.1736(8) 
                 2332(54) 
                 Perovskite, (002) 
               
               
                   
                  30.15(4) 
                  2.962(4) 
                  364(21) 
                 ITO, (112) 
               
               
                   
                 31.531(12) 
                 2.8351(10) 
                  941(34) 
                 Perovskite, (012) 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 10 mol % Csl &amp; 10 mol % PbCl2 
               
            
           
           
               
               
               
               
               
            
               
                   
                 2-theta 
                 d 
                 Height 
                 Peak Identity 
               
               
                   
                 (deg) 
                 (ang.) 
                 (cps) 
                 phase (miller index) 
               
               
                   
                   
               
               
                   
                 12.635(6) 
                  7.000(3) 
                  395(22) 
                 Pbl2, (001) 
               
               
                   
                 13.985(3) 
                 6.3272(13) 
                 13692(131) 
                 Perovskite, (001) 
               
               
                   
                 19.867(11) 
                  4.465(2) 
                   807(32) 
                 Perovskite, (011) 
               
               
                   
                 21.392(13) 
                  4.150(2) 
                   254(18) 
                 ITO, (112) 
               
               
                   
                  24.41(2) 
                  3.643(3) 
                   918(34) 
                 Perovskite, (111) 
               
               
                   
                 28.188(4) 
                 3.1633(4) 
                  6797(92) 
                 Perovskite, (002) 
               
               
                   
                  30.14(4) 
                  2.963(4) 
                   348(21) 
                 ITO, (112) 
               
               
                   
                 31.633(15) 
                 2.8262(13) 
                  1027(36) 
                 Perovskite, (012) 
               
               
                   
                   
               
            
           
         
       
     
     A geometrically expected x-ray diffraction pattern for cubic Pm3-m material with a lattice constant=6.3375 Å under Cu-Kα radiation is shown in Table 5. As can be seen from the data, the perovskite materials produced with 10 mol % Rb and 10 mol % Cl, 10 mol % Cs, and 10% Cs and 10% Cl each have diffraction patterns conforming to the expected pattern for a cubic, Pm3-m perovskite material. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Geometrically Expected Diffraction Pattern for Cubic 
               
               
                 Pm3-m, lattice constant = 6.3375Å; Cu-Kα Radiation) 
               
            
           
           
               
               
               
            
               
                   
                 d-spacing 
                   
               
               
                 2-Theta (degrees) 
                 (angstroms) 
                 Miller Index 
               
               
                   
               
            
           
           
               
               
               
            
               
                 13.963 
                 6.3375 
                 (0 0 1) 
               
               
                 19.796 
                 4.4813 
                 (0 1 1) 
               
               
                 24.306 
                 3.659 
                 (1 1 1) 
               
               
                 28.138 
                 3.1688 
                 (0 0 2) 
               
               
                 31.541 
                 2.8342 
                 (0 1 2) 
               
               
                   
               
            
           
         
       
     
     Enhanced Perovskite 
     So-called “layered” 2D perovskites are known to form when perovskites are formulated with organic cations having alkyl chains longer than the methylammonium and formamidinium cations described previously herein. Layered 2D perovskites include structures such as the Ruddlesden-Popper phase, Dion-Jacobson phase, and Aurivillius phase. For example, by substituting 1-butylammonium in place of the methylammonium or the other cations described above, during formation of a perovskite in a “one-step” method (not described herein), a Ruddlesden-Popper 2D perovskite may result. In such perovskites the 1-butylammonium prevents the perovskite from forming a full crystalline lattice, and instead causes the perovskite to form in “sheets” of perovskite having a single crystal structure in thickness.  FIG.  5    illustrates a structure of a Ruddlesden-Popper perovskite  5500  with a 1-butylammonium cation  5510 . As can be seen from  FIG.  5   , the “tails” of the butylammonium cation  5510  result in a separation between the lead and iodide portion of the perovskite material and other lead and iodide structures, resulting in “sheets” of 2D perovskites. Accordingly, introduction of “bulky organic” cations, such as 1-butylammonium or benzylammonium during formation of a perovskite material may be undesirable if the Ruddlesden-Popper form of the perovskite is not desired. 
     However, addition of a dilute amount of 1-butylammonium solution prior to annealing the perovskite material may result in a perovskite as shown in  FIG.  6   .  FIG.  6    illustrates an embodiment of a perovskite material  2000  with addition of an alkyl ammonium cation for surface passivation. In the illustrated embodiment, the surface of a formamidinium lead iodide (FAPbI 3 ) perovskite material  2010  is shown with 1-butylammonium cation  2020  at the surface. The 1-butylammonium cation, or other “bulky” organic cations as described herein, may diffuse into the perovskite material near the surface of the perovskite material crystal lattice, in some embodiments. In particular embodiments, the 1-butylammonium cation, or other “bulky” organic cations as described herein, may reside 50 nm or less into the perovskite material from the crystal lattice surfaces or grain boundaries. The inclusion of “bulky” organic cations, such as 1-butylammonium, near or at the surface of a perovskite material may result in the formula of the perovskite material deviating from the “ideal” stoichiometry of perovskite materials disclosed herein. For example, inclusion of such organic cations may cause the perovskite material to have a formula that is either substoichiometric or superstoichiometric with respect to the CMX 3  formula described herein. In this case, the general formula for the perovskite material may be expressed as C x M y X z , where x, y and z are real numbers. In some embodiments, a perovskite material may have the formula C′ 2 C n-1 M n X 3n-1 , where n is an integer. For example, when n=1 the perovskite material may have the formula C′ 2 MX 4 , when n=2 the perovskite material may have the formula C′ 2 CM 2 X 7 , when n=3 the perovskite material may have the formula C′ 2 C 2 M 3 X 10 , when n=4 the perovskite material may have the formula C′ 2 C 3 M 4 X 13 , and so on. As illustrated by  FIG.  30   , the n-value indicates the thickness of an inorganic metal halide sublattice of the perovskite material. A phase of the perovskite material having the formula C′ 2 C n-1 M n X 3n-1 , may form in regions where a bulky organic cation has diffused into, or otherwise entered into, the crystal lattice of a perovskite material. For example, such a phase may be present within 50 nanometers of a crystal lattice surface (e.g. a surface or grain boundary) of a perovskite material that has been formed including a bulky organic cation as disclosed herein. 
     The carbon “tails” of the 1-butyl ammonium ion may provide a protective property to the surface of the perovskite by effectively keeping other molecules away from the surface. In some embodiments, the alkyl group “tail” of the 1-butyl ammonium ion may be oriented away from or parallel to the surface of the perovskite material. In particular, the 1-butylammonium “tails” have hydrophobic properties, which prevents water molecules from contacting the surface of the perovskite and protects the surface of the perovskite material  2010  from water in the environment. Additionally, the 1-butylammonium cations may also act to passivate the surface and any grain boundaries or defects with the perovskite material  2010 . Passivation refers to an electrical characteristic that prevents charge accumulation or “trap states” at the surface or grain boundaries of the perovskite material  2010 . By acting to passivate portions of perovskite material  2010  the 1-butylammonium may facilitate improved charge transfer in and out of the perovskite material  2010  and improve the electrical properties of the photoactive layer. 
     In some embodiments, other organic cations may be applied in place of, or in combination with, 1-butylammonium. Examples of other “bulky organic” organic cations that may act as to surface passivate perovskite material, include, but are not limited to, ethylammonium, propylammonium, n-butylammonium; perylene n-butylamine-imide; butane-1,4-diammonium; 1-pentylammonium; 1-hexylammonium; poly(vinylammonium); phenylethylammonium; 3-phenyl-1-propylammonium; 4-phenyl-1-butyl ammonium; 1,3-dimethylbutylammonium; 3,3-dimethylbutylammonium; 1-heptylammonium; 1-octylammonium; 1-nonylammonium; 1-decylammonium; and 1-icosanyl ammonium. Additionally, bulky organic cations with a tail that contains one or more heteroatoms in addition to the cationic species, the heteroatom may coordinate with, bind to, or integrate with the perovskite material crystal lattice. A heteroatom may be any atom in the tail that is not hydrogen or carbon, including nitrogen, sulfur, oxygen, or phosphorous. 
     Other examples of “bulky” organic cations may include the following molecules functionalized with an ammonium group, phosphonium group, or other cationic group that may integrate into a surface “C-site of a perovskite material: benzene, pyridine, naphthalene, anthracene, xanthene, phenathrene, tetracene chrysene, tetraphene, benzo[c]phenathrene, triphenylene, pyrene, perylene, corannulene, coronene, substituted dicarboxylic imides, aniline, N-(2-aminoethyl)-2-isoindole-1,3-dione, 2-(1-aminoethyl)naphthalene, 2-triphenylene-O-ethylamine ether, benzyl amine, benzylammonium salts, N-n-butyl-N′-4-aminobutylperylene-3,4,9,10-bis(dicarboximide), 1-(4-alkylphenyl)methanamine, 1-(4-alkyl-2-phenyl)ethanamine, 1-(4-alkylphenyl)methanamine, 1-(3-alkyl-5-alkylphenyl)methanamine, 1-(3-alkyl-5-alkyl-2-phenyl)ethanamine, 1-(4-alkyl-2-phenyl)ethanamine, 2-Ethylamine-7-alkyl-Naphthalene, 2-Ethylamine-6-alkyl-Naphthalene, 1-Ethylamine-7-alkyl-Naphthalene, 1-Ethylamine-6-alkyl-Naphthalene, 2-Methylamine-7-alkyl-Naphthalene, 2-Methylamine-6-alkyl-Naphthalene, 1-Methylamine-7-alkyl-Naphthalene, 1-Methylamine-6-alkyl-Naphthalene, N-n-aminoalkyl-N′-4-aminobutylperylene-3,4,9,10-bis(dicarboximide), 1-(3-Butyl-5-methoxybutylphenyl)methanamine, 1-(4-Pentylphenyl)methanamine, 1-[4-(2-Methylpentyl)-2-phenyl]ethanamine, 1-(3-Butyl-5-pentyl-2-phenyl)ethanamine, 2-(5-[4-Methylpentyl]-2-naphthyl)ethanamine, N-7-tridecyl-N′-4-aminobutylperylene-3,4,9,10-bis(dicarboximide), N-n-heptyl-N′-4-aminobutylperylene-3,4,9,10-bis(dicarboximide), 2-(6-[3-Methoxylpropyl]-2-naphthyl)ethanamine.  FIGS.  17 - 28    provide illustrations of the structures of these organic molecules, according to certain embodiments. With respect to  FIGS.  17  and  18   , each “R-group,” R x  may be any of ═H, R′, Me, Et, Pr, Ph, Bz, F, Cl, Br, I, NO 2 , OR′, NR′ 2 , SCN, CN, N 3 , SR′, where R′ may be any alkyl, alkenyl, or alkynyl chain. Additionally, at least one of the illustrated R x  groups may be (CH 2 ) n EX y  or (CH 2 ) n C(EX y ) 2  where n and y=0,1,2, or greater and n and y may or may not be equal. Further, with respect to  FIG.  19   , the illustrated molecules may include any hydrohalide of each illustrated amine, for example benzylammonium salts, where the illustrated X group may be F, Cl, Br, I, SCN, CN, or any other pseudohalide. Other non-halide acceptable anions may include: nitrate, nitrite, carboxylate, acetate, acetonyl acetonate, formate, oxalate, sulfate, sulfite, thiosulfate, phosphate, tetrafluoroborate, hexafluorophosphate, tetra(perfluorophenyl) borate, hydride, oxide, peroxide, hydroxide, nitride, arsenate, arsenite, perchlorate, carbonate, bicarbonate, chromate, dichromate, iodate, bromate, chlorate, chlorite, hypochlorite, hypobromite, cyanide, cyanate, isocyanate, fulminate, thiocyanate, isothiocyanate, azide, tetracarbonylcobaltate, carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide, tricyanomethanide, amide, and permanganate. Suitable R groups may also include, but are not limited to: hydrogen, methyl, ethyl, propyl, butyl, pentyl group or isomer thereof; any alkane, alkene, or alkyne CxHy, where x=1-20, y=1-42, cyclic, branched or straight-chain; alkyl halides, CxHyXz, x=1-20, y=0-42, z=1-42, X═F, Cl, Br, or I; any aromatic group (e.g., phenyl, alkylphenl, alkoxyphenyl, pyridine, naphthalene); cyclic complexes where at least one nitrogen is contained within the ring (e.g., pyridine, pyrrole, pyrrolidine, piperidine, tetrahydroquinoline); any sulfur-containing group (e.g., sulfoxide, thiol, alkyl sulfide); any nitrogen-containing group (nitroxide, amine); any phosphorous containing group (phosphate); any boron-containing group (e.g., boronic acid); any organic acid (e.g., acetic acid, propanoic acid); and ester or amide derivatives thereof; any amino acid (e.g., glycine, cysteine, proline, glutamic acid, arginine, serine, histidine, 5-ammoniumvaleric acid) including alpha, beta, gamma, and greater derivatives; any silicon containing group (e.g., siloxane); and any alkoxy or group, —OCxHy, where x=0-20, y=1-42. 
     Additionally, in some embodiments, the bulky organic cation may passivate grain boundaries and surface defects in the perovskite material.  FIG.  7    illustrates an example embodiment of a perovskite material layer  3000  with 1-butylammonium  3020  passivating both the surface and grain boundaries  3015  of a bulk perovskite material  3010 . As described above, the alkyl tails of these ions may also form a hydrophobic layer which repels water and other polar species and impedes such species from reaching the surface of the perovskite material. As can be seen in  FIG.  7   , the “tails” of the bulky organic cations may not be chemically connected (e.g., covalently or ionically bonded) to the surface or grain boundaries  3015  of the perovskite material layer  3000 . As used herein, “tails” of any bulky organic cation refers to the non-ionic carbon structure of the bulky organic cation. For example, the tail of 1-butylammonium is the butyl group and the tail of benzylammonium is the benzyl group. 
     The tails of the bulky organic cation may also assume other arrangements with respect to the surface or grain boundary of a perovskite material. Generally, the cationic “head” of a bulky organic cation will not diffuse more than 50 nanometers past the surface or a grain boundary of a perovskite material. The tail may interact weakly with the perovskite material and be oriented away from the perovskite material crystal grain surface. The tail may have an intermolecular interaction (e.g., dipole-dipole or hydrogen bonding) with the perovskite material crystal grain surface resulting in a configuration where the tail is oriented towards the perovskite material crystal grain surface. In some embodiments, the tails of some bulky organic cations present in the perovskite material may not interact with the surfaces or grain boundaries of the perovskite material and the tails of other bulky organic cations in the perovskite material may interact with the surfaces or grain boundaries of the perovskite material. The tail may contain a heteroatom or anion (i.e., a zwitterion) with at least one electron lone pair that may interact covalently (i.e., a coordination covalent bond) with the perovskite material crystal grain surface via a metal atom (e.g., Pb, Sn, Ge, In, Bi, Cu, Ag, Au) present in the perovskite material. The tail may also include a cationic species, such as diammonium butane as described herein, that may incorporate into the perovskite material by substituting on at least two “C” cation sites (such as formamidinium). A tail including a cationic species may also bridge two layers of a 2D perovskite material, lie prone across the perovskite material crystal grain surface, or orient away from the perovskite material crystal grain surface in a similar manner to that described with respect to a non-ionic tail. In another embodiment, a bulky organic cation having a sufficiently bulky tail, such as an imidazolium cation, may simply reside on the perovskite surface or grain boundary without diffusing into the perovskite material. 
     Additionally, in other embodiments, the bulky organic cations with tail groups that vary in length or size may be applied to the perovskite to passivate grain boundaries and surface defects in the perovskite material.  FIG.  8    illustrates an example embodiment of a perovskite material layer  4000  with a combination of 1-butylammonium  4020 , 1-nonylammonium  4021 , 1-heptylammonium  4022 , and 1-hexyl ammonium  4023  passivating both the surface and grain boundaries  4015  of a bulk perovskite material  4010 . In particular embodiments, any mixture of the alkylammonium compounds identified above may be applied to a perovskite material as described herein.  FIG.  8    illustrates an example embodiment of a perovskite material layer  4000  with a combination of 1-butylammonium  4020 , 1-nonylammonium  4021 , 1-heptylammonium  4022 , and 1-hexyl ammonium  4023  passivating both the surface and grain boundaries  4015  of a bulk perovskite material  4010 . In particular embodiments, any mixture of the alkylammonium compounds identified above may be applied to a perovskite material as described herein. In some embodiments bulky organic cations may include a benzyl group.  FIG.  8 A  illustrates an example embodiment of a perovskite material layer  4500  with a variety of bulky organic cations containing benzyl groups passivating both the surface and grain boundaries  4515  of a bulk perovskite material  4510 . 
     Addition of a 1-butylammonium surface coating to a perovskite material as described above has been shown to increase the high temperature durability of the perovskite in damp environments.  FIG.  9    shows a comparison of images taken of a perovskite material with and without a 1-butylammonium (“BAI”) surface coating over a period of 48 days. Both perovskite materials had the same composition and were exposed to an environment having a temperature of 85° C. at 55% relative humidity for 48 days. As can be seen from the photographs, the perovskite material having no 1-butylammonium surface coating lightens in color significantly after one day of exposure to the environment, indicating that the perovskite material has degraded significantly. The perovskite material having the 1-butylammonium surface coating shows a gradual lightening of color over 48 days and remains partially dark after 48 days. This indicates that the perovskite material with the 1-butylammonium surface coating is more robust than a perovskite material without a 1-butylammonium surface coating during extended exposure to a high-temperature environment. 
       FIG.  10    shows a comparison of images taken of a perovskite material with and without a 1-butylammonium (“BAI”) surface coating over a period of seven days. Both perovskite materials had the same composition and were exposed to an environment having a temperature of 85° C. at 0% relative humidity for 7 days. As can be seen from the photographs, the perovskite material having no 1-butylammonium surface coating lightens in color significantly after one day of exposure to the environment, indicating that the perovskite material has degraded significantly. The perovskite material having the 1-butylammonium surface coating shows very little change in color after seven days. This indicates that the perovskite material with the 1-butylammonium surface coating did not completely break down during extended exposure to a high-temperature, high-humidity environment. 
     In other embodiments, perylene n-butylamine-imide may be applied to the surface of a perovskite material as described above with respect to 1-butylammonium.  FIGS.  11 A-D  illustrate various perylene monoimides and diimides that may be applied to the surface of a perovskite material according to the present disclosure.  FIG.  12    illustrates an embodiment of a perovskite material  2500  with addition of an alkyl ammonium cation for surface passivation. In the illustrated embodiment, the surface of a formamidinium lead iodide (FAPbI 3 ) perovskite material  2510  is shown with perylene n-butylamine-imide  2520  at the surface. As with the 1-butylammonium illustrated in  FIG.  6   , the carbon “tails” of the perylene n-butylamine-imide ion may provide a protective property to the surface of the perovskite by effectively keeping other molecules away from the surface. In particular, the perylene n-butylamine-imide “tails” have hydrophobic properties, which prevents water molecules from contacting the surface of the perovskite and protects the surface of the perovskite material  2510  from water in the environment. Additionally, the perylene n-butylamine-imide cations may also act to passivate the surface and any grain boundaries or defects with the perovskite material  2510 . By acting to passivate portions of perovskite material  2510  the perylene n-butylamine-imide may facilitate improved charge transfer in and out of the perovskite material  2510  and improve the electrical properties of the photoactive layer. 
     An example method for depositing the 1-butylammonium prior to annealing the perovskite material is described below. 
     First, a lead halide precursor ink is formed. An amount of lead halide may be massed in a clean, dry vessel in a controlled atmosphere environment (e.g., controlled atmosphere box with glove-containing portholes allows for materials manipulation in an air-free environment). Suitable lead halides include, but are not limited to, lead (II) iodide, lead (II) bromide, lead (II) chloride, and lead (II) fluoride. The lead halide may comprise a single species of lead halide or it may comprise a lead halide mixture in a precise ratio. In certain embodiments, the lead halide mixture may comprise any binary, ternary, or quaternary ratio of 0.001-100 mol % of iodide, bromide, chloride, or fluoride. In one embodiment, the lead halide mixture may comprise lead (II) chloride and lead (II) iodide in a ratio of about 10:90 mol:mol. In other embodiments, the lead halide mixture may comprise lead (II) chloride and lead (II) iodide in a ratio of about 5:95, about 7.5:92.5, or about 15:85 mol:mol. 
     Alternatively, other lead salt precursors may be used in conjunction with or in lieu of lead halide salts to form the precursor ink. Suitable precursor salts may comprise any combination of lead (II) or lead(IV) and the following anions: nitrate, nitrite, carboxylate, acetate, acetonyl acetonate, formate, oxalate, sulfate, sulfite, thiosulfate, phosphate, tetrafluoroborate, hexafluorophosphate, tetra(perfluorophenyl) borate, hydride, oxide, peroxide, hydroxide, nitride, arsenate, arsenite, perchlorate, carbonate, bicarbonate, chromate, dichromate, iodate, bromate, chlorate, chlorite, hypochlorite, hypobromite, cyanide, cyanate, isocyanate, fulminate, thiocyanate, isothiocyanate, azide, tetracarbonylcobaltate, carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide, tricyanomethanide, amide, and permanganate. 
     The precursor ink may further comprise a lead (II) or lead (IV) salt in mole ratios of 0 to 100% to the following metal ions Be, Mg, Ca, Sr, Ba, Fe, Cd, Co, Ni, Cu, Ag, Au, Hg, Sn, Ge, Ga, In, Tl, Sb, Bi, Ti, Zn, Cd, Hg, and Zr as a salt of the aforementioned anions. 
     A solvent may then be added to dissolve the lead solids to form the lead halide precursor ink. Suitable solvents include, but are not limited to, dry N-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone, dimethylformamide, dialkylformamide, dimethylsulfoxide (DMSO), methanol, ethanol, propanol, butanol, tetrahydrofuran, formamide, tert-butylpyridine, pyridine, alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, and combinations thereof. In one embodiment, the lead solids are dissolved in dry dimethylformamide (DMF). The lead solids may be dissolved at a temperature between about 20° C. to about 150° C. In one embodiment, the lead solids are dissolved at about 85° C. The lead solids may be dissolved for as long as necessary to form a solution, which may take place over a time period up to about 72 hours. The resulting solution forms the base of the lead halide precursor ink. In some embodiments, the lead halide precursor ink may have a lead halide concentration between about 0.001M and about 10M. In one embodiment, the lead halide precursor ink has a lead halide concentration of about 1 M. 
     Optionally, certain additives may be added to the lead halide precursor ink to affect the final perovskite crystallinity and stability. In some embodiments, the lead halide precursor ink may further comprise an amino acid (e.g., 5-aminovaleric acid, histidine, glycine, lysine), an amino acid hydrohalide (e.g., 5-amino valeric acid hydrochloride), an IFL surface-modifying (SAM) agent (such as those discussed earlier in the specification), or a combination thereof. In one embodiment, formamidinium chloride may be added to the lead halide precursor ink. In other embodiments, the halide of any cation discussed earlier in the specification may be used. In some embodiments, combinations of additives may be added to the lead halide precursor ink including, for example, the combination of formamidinium chloride and 5-amino valeric acid hydrochloride. 
     The additives, including formamidinium chloride and/or 5-amino valeric acid hydrochloride may be added to the lead halide precursor ink at various concentrations depending on the desired characteristics of the resulting perovskite material. In one embodiment, the additives may be added in a concentration of about 1 nM to about 1 M. In another embodiment, the additives may be added in a concentration of about 1 μM to about 1 M. In another embodiment, the additives may be added in a concentration of about 1 μM to about 1 mM. 
     In some embodiments, a Group 1 metal halide solution is formed to be added to the lead halide precursor ink. An amount of Group 1 metal halide may be massed in a clean, dry vessel in a controlled atmosphere environment. Suitable Group 1 metal halides include, but are not limited to, cesium iodide, cesium bromide, cesium chloride, cesium fluoride, rubidium iodide, rubidium bromide, rubidium chloride, rubidium fluoride, lithium iodide, lithium bromide, lithium chloride, lithium fluoride, sodium iodide, sodium bromide, sodium chloride, sodium fluoride, potassium iodide, potassium bromide, potassium chloride, potassium fluoride. The Group 1 metal halide may comprise a single species of Group 1 metal halide or it may comprise a Group 1 metal halide mixture in a precise ratio. In one embodiment the Group 1 metal halide may comprise cesium iodide. In another embodiment the Group 1 metal halide may comprise rubidium iodide. In another embodiment the Group 1 metal halide may comprise sodium iodide. In another embodiment the Group 1 metal halide may comprise potassium iodide. 
     Alternatively, other Group 1 metal salt precursors may be used in conjunction with or in lieu of Group 1 metal halide salts to form a Group 1 metal salt solution. Suitable precursor Group 1 metal salts may comprise any combination of Group 1 metals and the following anions: nitrate, nitrite, carboxylate, acetate, formate, oxalate, sulfate, sulfite, thiosulfate, phosphate, tetrafluoroborate, hexafluorophosphate, tetra(perfluorophenyl) borate, hydride, oxide, peroxide, hydroxide, nitride, arsenate, arsenite, perchlorate, carbonate, bicarbonate, chromate, dichromate, iodate, bromate, chlorate, chlorite, hypochlorite, hypobromite, cyanide, cyanate, isocyanate, fulminate, thiocyanate, isothiocyanate, azide, tetracarbonylcobaltate, carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide, tricyanomethanide, amide, and permanganate. 
     A solvent may then be added to the vessel to dissolve the Group 1 metal halide solids to form the Group 1 metal halide solution. Suitable solvents include, but are not limited to, dry N-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone, dimethylformamide (DMF), dialkylformamide, dimethylsulfoxide (DMSO), methanol, ethanol, propanol, butanol, tetrahydrofuran, formamide, tert-butylpyridine, pyridine, alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, and combinations thereof. In one embodiment, the lead solids are dissolved in dry dimethylsulfoxide (DMSO). The Group 1 metal halide solids may be dissolved at a temperature between about 20° C. to about 150° C. In one embodiment, the Group 1 metal halide solids are dissolved at room temperature (i.e. about 25° C.). The Group 1 metal halide solids may be dissolved for as long as necessary to form a solution, which may take place over a time period up to about 72 hours. The resulting solution forms the Group 1 metal halide solution. In some embodiments, the Group 1 metal halide solution may have a Group 1 metal halide concentration between about 0.001M and about 10M. In one embodiment, the Group 1 metal halide solution has a Group 1 metal halide concentration of about 1 M. In some embodiments, the Group 1 metal halide solution may further comprise an amino acid (e.g., 5-aminovaleric acid, histidine, glycine, lysine), an amino acid hydrohalide (e.g., 5-amino valeric acid hydrochloride), an IFL surface-modifying (SAM) agent (such as those discussed earlier in the specification), or a combination thereof. 
     Next, the lead halide solution and the Group 1 metal halide solution are mixed to form a thin-film precursor ink. The lead halide solution and Group 1 metal halide solution may be mixed in a ratio such that the resulting thin-film precursor ink has a molar concentration of the Group 1 metal halide that is between 0% and 25% of the molar concentration of the lead halide. In particular embodiments, the thin-film precursor ink may have a molar concentration of the Group 1 metal halide that is 1% of the molar concentration of the lead halide. In particular embodiments, the thin-film precursor ink may have a molar concentration of the Group 1 metal halide that is 5% of the molar concentration of the lead halide. In particular embodiments, the thin-film precursor ink may have a molar concentration of the Group 1 metal halide that is 10% of the molar concentration of the lead halide. In particular embodiments, the thin-film precursor ink may have a molar concentration of the Group 1 metal halide that is 15% of the molar concentration of the lead halide. In particular embodiments, the thin-film precursor ink may have a molar concentration of the Group 1 metal halide that is 20% of the molar concentration of the lead halide. In particular embodiments, the thin-film precursor ink may have a molar concentration of the Group 1 metal halide that is 25% of the molar concentration of the lead halide. In some embodiments the lead halide solution and the Group 1 metal halide solution may be stirred or agitated during or after mixing. 
     Optionally, in certain embodiments, water may be added to the lead halide precursor ink. By way of explanation, and without limiting the disclosure to any particular theory or mechanism, the presence of water affects perovskite thin-film crystalline growth. Under normal circumstances, water may be absorbed as vapor from the air. However, it is possible to control the perovskite PV crystallinity through the direct addition of water to the lead halide precursor ink in specific concentrations. Suitable water includes distilled, deionized water, or any other source of water that is substantially free of contaminants (including minerals). It has been found, based on light I-V sweeps, that the perovskite PV light-to-power conversion efficiency may nearly triple with the addition of water compared to a completely dry device. 
     The water may be added to the lead halide precursor ink at various concentrations depending on the desired characteristics of the resulting perovskite material. In one embodiment, the water may be added in a concentration of about 1 nL/mL to about 1 mL/mL. In another embodiment, the water may be added in a concentration of about 1 μL/mL to about 0.1 mL/mL. In another embodiment, the water may be added in a concentration of about 1 μL/mL to about 20 μL/mL. 
     The lead halide precursor ink or the thin film precursor ink may then be deposited on the desired substrate. Suitable substrate layers may include any of the substrate layers identified earlier in this disclosure. As noted above, the lead halide precursor ink or the thin film precursor ink may be deposited through a variety of means, including but not limited to, drop casting, spin casting, slot-die printing, screen printing, or ink-jet printing. In certain embodiments, the lead halide precursor ink or the thin film precursor ink may be spin-coated onto the substrate at a speed of about 500 rpm to about 10,000 rpm for a time period of about 5 seconds to about 600 seconds. In one embodiment, the lead halide precursor ink or the thin film precursor ink may be spin-coated onto the substrate at about 3000 rpm for about 30 seconds. In some embodiments, multiple subsequent depositions of the precursor ink may be made to form a thin-film layer. The lead halide precursor ink or the thin film precursor ink may be deposited on the substrate at an ambient atmosphere in a humidity range of about 0% relative humidity to about 50% relative humidity. The lead halide precursor ink or the thin film precursor ink may then be allowed to dry in a substantially water-free atmosphere, i.e., less than 30% relative humidity, to form a thin film. 
     After deposition of the lead halide precursor or thin film precursor, a bulky organic cation as described above (e.g. benzylammonium, phenylethylammonium, ethylammonium, propylammonium, n-butylammonium; butane-1,4-diammonium; 1-pentylammonium; 1-hexylammonium; poly(vinylammonium); phenylethylammonium; 3-phenyl-1-propylammonium; 4-phenyl-1-butylammonium; 1,3-dimethylbutylammonium; 3,3-dimethylbutylammonium; 1-heptylammonium; 1-octylammonium; 1-nonylammonium; 1-decylammonium; 1-icosanyl ammonium; or any other bulky cation described herein or illustrated in  FIGS.  17 - 28   ) salt solution may be applied to the thin film resulting from the deposition of the lead salt precursor and the second salt precursor. Bulky organic salts may include halide, nitrate, nitrite, carboxylate, acetate, acetonyl acetonate, formate, oxalate, sulfate, sulfite, thiosulfate, phosphate, tetrafluoroborate, hexafluorophosphate, tetra(perfluorophenyl) borate, hydride, oxide, peroxide, hydroxide, nitride, arsenate, arsenite, perchlorate, carbonate, bicarbonate, chromate, dichromate, iodate, bromate, chlorate, chlorite, hypochlorite, hypobromite, cyanide, cyanate, isocyanate, fulminate, thiocyanate, isothiocyanate, azide, tetracarbonylcobaltate, carbamoyldicyanomethanide, dicyanonitrosomethanide, dicyanamide, tricyanomethanide, amide, and/or permanganate salts of any of the preceding cations. The bulky organic cation salt solution may be formed by dissolving a bulky organic cation salt in a solvent such as an alcohol, dry N-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone, dimethylformamide (DMF), dialkylformamide, dimethylsulfoxide (DMSO), methanol, ethanol, propanol, butanol, tetrahydrofuran, formamide, tert-butylpyridine, pyridine, alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, and combinations thereof. In a particular embodiment, the bulky organic cation salt may be dissolved in isopropyl alcohol. In certain embodiments, the bulky organic cation salt solution may have a concentration between 0.0001 M and 1.0 M of the bulky organic cation salt. In other embodiments, the bulky organic cation salt solution may have a concentration between 0.01 M and 0.1 M of the bulky organic cation salt. In particular embodiments, the bulky organic cation salt solution may have a concentration of between 0.02 and 0.05 M of the bulky organic cation salt. In a particular embodiment, the bulky organic cation salt solution may have a concentration of approximately 0.05 M of the bulky organic cation salt. The bulky organic cation salt solution may be deposited onto the perovskite material precursor thin film by any method described herein with respect to solution deposition. These methods may include, spray coating, drop casting, spin casting, slot-die printing, screen printing, gravure printing, or ink-jet printing. In one embodiment, the bulky organic cation salt may be 1-butylammonium iodide. In another embodiment, the bulky organic cation salt may be benzylammonium iodide. In yet another embodiment, the bulky organic cation salt may be phenylethylammonium iodide. 
     The thin film may then be thermally annealed for a time period up to about 24 hours at a temperature of about 20° C. to about 300° C. In one embodiment, the thin film may be thermally annealed for about ten minutes at a temperature of about 50° C. The perovskite material active layer may then be completed by a conversion process in which the precursor film is submerged or rinsed with a solution comprising a solvent or mixture of solvents (e.g., DMF, isopropanol, methanol, ethanol, butanol, chloroform chlorobenzene, dimethylsulfoxide, water) and salt (e.g., methylammonium iodide, formamidinium iodide, guanidinium iodide, 1,2,2-triaminovinylammonium iodide, 5-aminovaleric acid hydroiodide) in a concentration between 0.001M and 10M. In certain embodiments, the thin films may also be thermally post-annealed in the same fashion as in the first line of this paragraph. 
     After the thin film is deposited and, in some embodiments, annealed, a second salt precursor (e.g., formamidinium iodide, formamidinium thiocyanate, or guanidinium thiocyanate) may be deposited onto the lead salt thin film, where the thin film may have a temperature about equal to ambient temperature or have a controlled temperature between 0° C. and 500° C. The second salt precursor may be deposited at ambient temperature or at elevated temperature between about 25° C. and 125° C. The second salt precursor may be deposited by a variety of methods known in the art, including but not limited to spin-coating, slot-die printing, ink-jet printing, gravure printing, screen printing, sputtering, PE-CVD, thermal evaporation, or spray coating. In some embodiments, multiple subsequent depositions of the second salt solution may be made to form a thin-film layer. In some embodiments the second salt precursor may be a solution containing one or more solvents. For example, the second salt precursor may contain one or more of dry N-cyclohexyl-2-pyrrolidone, alkyl-2-pyrrolidone, dimethylformamide, dialkylformamide, dimethylsulfoxide (DMSO), methanol, ethanol, propanol, butanol, tetrahydrofuran, formamide, tert-butylpyridine, pyridine, alkylpyridine, pyrrolidine, chlorobenzene, dichlorobenzene, dichloromethane, chloroform, and combinations thereof. 
     In some embodiments, any bulky organic cation salt as described herein may be combined with the second salt solution prior to deposition of the second salt solution. In particular embodiments, a bulky organic cation salt solution may be prepared as described above and mixed with the second salt solution prior to deposition of the second salt solution. For example, the bulky organic cation salt solution may have a concentration between 0.0001 M and 1.0 M of the bulky organic cation salt. In other embodiments, the bulky organic cation salt solution may have a concentration between 0.01 M and 0.1 M of the bulky organic cation salt. In particular embodiments, the bulky organic cation salt solution may have a concentration of between 0.02 and 0.05 M of the bulky organic cation salt. In a particular embodiment, the bulky organic cation salt solution may have a concentration of approximately 0.05 M of the bulky organic cation salt. In other embodiments, a bulky organic cation salt solution may be deposited onto a lead halide thin film formed after deposition of a lead halide precursor ink or thin film precursor ink. In another embodiment, a bulky organic cation salt solution may be deposited onto a perovskite precursor thin film after deposition of the second salt solution. 
     Finally, the substrate with the perovskite material precursor thin film may be annealed. Annealing the substrate may convert the lead salt precursor and second salt precursor to a perovskite material, (e.g. FAPbI 3 , GAPb(SCN) 3 , FASnI 3 ), with a surface passivating layer of the bulky organic cation. Annealing may be performed in a variety of atmospheres at ambient pressure (e.g. about one atmosphere (760 Torr), depending on elevation and atmospheric conditions) or at pressures less than atmospheric or ambient (e.g., 1 mTorr to 500 mTorr). An annealing atmosphere may comprise ambient air, a controlled humidity environment (e.g., 0-100 g H 2 O/m 3  of gas), pure argon, pure nitrogen, pure oxygen, pure hydrogen, pure helium, pure neon, pure krypton, pure CO 2  or any combination of the preceding gases. A controlled humidity environment may include an environment in which the absolute humidity or the % relative humidity is held at a fixed value, or in which the absolute humidity or the % relative humidity varies according to predetermined set points or a predetermined function. In particular embodiments, annealing may occur in a controlled humidity environment having a % relative humidity greater than or equal to 0% and less than or equal to 50%. In other embodiments, annealing may occur in a controlled humidity environment containing greater than or equal to 0 g H 2 O/m 3  gas and less than or equal to 20 g H 2 O/m 3  gas. In some embodiments, annealing may occur at a temperature greater than or equal to 50° C. and less than or equal to 300° C. 
     For example, in a particular embodiment, a FAPbI 3  perovskite material may be formed by the following process. First a lead (II) halide precursor comprising about a 90:10 mole ratio of PbI 2  to PbCl 2  dissolved in anhydrous DMF may be deposited onto a substrate by spin-coating, blade coating, or slot-die printing. The lead halide precursor ink may be allowed to dry in a substantially water-free atmosphere, i.e., less than 30% relative humidity or 17 g H 2 O/m 3 , for approximately one hour (+15 minutes) to form a thin film. The thin film may be subsequently thermally annealed for about ten minutes at a temperature of about 50° C. (±10° C.). In other embodiments, the lead halide precursor may be deposited by ink-jet printing, gravure printing, screen printing, sputtering, PE-CVD, atomic-layer deposition, thermal evaporation, or spray coating. Next, a 1-butylammonium salt solution having a concentration of 0.05 M in isopropyl alcohol may be deposited onto the lead halide thin film. Next, a formamidinium iodide precursor comprising a 15-100 mg/mL concentration of formamidinium iodide dissolved in anhydrous isopropyl alcohol may be deposited onto the lead halide thin film by spin coating or blade coating. In other embodiments, the formamidinium iodide precursor may be deposited by ink-jet printing, gravure printing, screen printing, slot-die printing, sputtering, PE-CVD, atomic-layer deposition, thermal evaporation, or spray coating. Next, the substrate may be annealed at about 25% relative humidity (about 4 to 7 g H 2 O/m 3  gas) and between about 100° C. and 200° C. to form a formamidinium lead iodide (FAPbI 3 ) perovskite material, with a surface layer of 1-butylammonium. In alternative embodiments, the 1-butylammonium salt solution may be deposited onto the thin film formed after deposition of the formamidinium iodide precursor. In another embodiment, the 1-butylammonium salt solution may be combined with the lead halide precursor ink prior to deposition of the lead halide precursor ink. In yet another embodiment, the 1-butylammonium salt solution may be combined with the formamidinium iodide precursor prior to deposition of the formamidinium iodide precursor. In yet another embodiment, the 1-butylammonium salt solution may be deposited onto the thin film following deposition of the formamidinium iodide precursor and prior to annealing the thin film and substrate. In yet another embodiment, the 1-butylammonium salt solution may be deposited onto the thin film after annealing the thin film and substrate. 
     In other embodiments, using the process described above with a lead (II) iodide solution, a cesium iodide solution, a methylammonium (MA) iodide salt solution, and a 1-butylammonium salt solution may result in a perovskite material having the formula of Cs i MAPbI 3 , where i equals a number between 0 and 1 with a surface layer of 1-butylammonium. As another example, the using a lead (II) iodide solution, a rubidium iodide solution, a formamidinium (FA) iodide salt solution, and a 1-butylammonium salt solution may result in a perovskite material having the formula of Rb i FAPbI 3 , where i equals a number between 0 and 1 with a surface layer of 1-butylammonium layer. As another example, using the process described above with a lead (II) iodide solution, a cesium iodide solution, a formamidinium (FA) iodide salt solution, and a 1-butylammonium salt solution may result in a perovskite material having the formula of Cs i FAPbI 3 , where i equals a number between 0 and 1 with a surface layer of 1-butylammonium layer. As another example, the using a lead (II) iodide solution, a potassium iodide solution, a formamidinium (FA) iodide salt solution, and a 1-butylammonium salt solution may result in a perovskite material having the formula of K i FAPbI 3 , where i equals a number between 0 and 1 with a surface layer of 1-butylammonium layer. As another example, the using a lead (II) iodide solution, a sodium iodide solution, a formamidinium (FA) iodide salt solution, and a 1-butylammonium salt solution may result in a perovskite material having the formula of Na i FAPbI 3 , where i equals a number between 0 and 1 with a surface layer of 1-butylammonium layer. As another example, the using a lead (II) iodide-lead (II) chloride mixture solution, a cesium iodide solution, a formamidinium (FA) iodide salt solution, and a 1-butylammonium salt solution may result in a perovskite material having the formula of Cs i FAPbI 3-y Cl y , where i equals a number between 0 and 1 and y represents a number between 0 and 3 with a surface layer of 1-butylammonium layer. 
     In another embodiment, a FAPbI 3  perovskite material may be formed by the following process. First a lead (II) halide precursor ink comprising about a 90:10 mole ratio of PbI 2  to PbCl 2  dissolved in anhydrous DMF may be deposited onto a substrate by spin-coating, blade coating, or slot-die printing. The lead halide precursor ink may be allowed to dry in a substantially water-free atmosphere, i.e., less than 30% relative humidity or 17 g H 2 O/m 3 , for approximately one hour (+15 minutes) to form a thin film. The thin film may be subsequently thermally annealed for about ten minutes at a temperature of about 50° C. (±10° C.). In other embodiments, the lead halide precursor may be deposited by ink-jet printing, gravure printing, screen printing, sputtering, PE-CVD, atomic-layer deposition, thermal evaporation, or spray coating. Next, a formamidinium iodide precursor comprising a 15-60 mg/mL concentration of formamidinium iodide dissolved in anhydrous isopropyl alcohol may be deposited onto the lead halide thin film by spin coating or blade coating. In other embodiments, the formamidinium iodide precursor may be deposited by ink-jet printing, gravure printing, screen printing, slot-die printing, sputtering, PE-CVD, atomic-layer deposition, thermal evaporation, or spray coating. After depositing the lead halide precursor and formamidinium iodide precursor, a benzylammonium salt solution having a concentration of 0.04 M in isopropyl alcohol may be deposited onto the perovskite material precursor thin film. Next, the substrate may be annealed at about 25% relative humidity (about 4 to 7 g H 2 O/m 3  gas) and between about 100° C. and 200° C. to form a formamidinium lead iodide (FAPbI 3 ) perovskite material, with a surface layer of benzylammonium. In particular embodiments, the benzylammonium salt solution may be deposited onto the lead halide thin film prior to deposition of the formamidinium iodide precursor. In another embodiment, the benzylammonium salt solution may be combined with the lead halide precursor ink prior to deposition of the lead halide precursor ink. In yet another embodiment, the benzylammonium salt solution may be combined with the formamidinium iodide precursor prior to deposition of the formamidinium iodide precursor. In some embodiments, the resulting perovskite material may have a cubic crystal structure in the bulk material away from the surface. The presence of bulky organic cations near the surface of the perovskite material may result in a non-cubic crystal structure near the surface of the perovskite material. 
     In other embodiments, using the process described above with a lead (II) iodide solution, a cesium iodide solution, a methylammonium (MA) iodide salt solution, and a 1-butylammonium salt solution may result in a perovskite material having the formula of Cs i MAPbI 3 , where i equals a number between 0 and 1 with a surface layer of benzylammonium. As another example, using the process described above with a lead (II) iodide solution, a rubidium iodide solution, a formamidinium (FA) iodide salt solution, and a benzylammonium salt solution may result in a perovskite material having the formula of Rb i FAPbI 3 , where i equals a number between 0 and 1 with a surface layer of benzylammonium layer. As another example, using the process described above with a lead (II) iodide solution, a cesium iodide solution, a formamidinium (FA) iodide salt solution, and a benzylammonium salt solution may result in a perovskite material having the formula of Cs i FAPbI 3 , where i equals a number between 0 and 1 with a surface layer of benzylammonium layer. As another example, using the process described above with a lead (II) iodide solution, a potassium iodide solution, a formamidinium (FA) iodide salt solution, and a benzylammonium salt solution may result in a perovskite material having the formula of K i FAPbI 3 , where i equals a number between 0 and 1 with a surface layer of benzylammonium layer. As another example, using the process described above with a lead (II) iodide solution, a sodium iodide solution, a formamidinium (FA) iodide salt solution, and a benzylammonium salt solution may result in a perovskite material having the formula of Na i FAPbI 3 , where i equals a number between 0 and 1 with a surface layer of benzylammonium r. As another example, using the process described above with a lead (II) iodide-lead (II) chloride mixture solution, a cesium iodide solution, a formamidinium (FA) iodide salt solution, and a benzylammonium salt solution may result in a perovskite material having the formula of Cs i FAPbI 3-y Cl y , where i equals a number between 0 and 1 and y represents a number between 0 and 3 with a surface layer of benzylammonium layer. 
     A method for producing a perovskite material with benzylammonium is described below. First, a lead iodide precursor ink is prepared by dissolving PbI 2 , PbCl 2 , and cesium iodide (CsI) in a mixture of DMF and DMSO solvents. To prepare the lead iodide precursor in, a 1.5 M CSI/DMSO solution is prepared by dissolving CsI in DMSO. The CSI/DMSO solution may be prepared, in a particular embodiment, by stirring CsI into DMSO at a ratio of 1.5 mmol of CsI per 1.0 mL of anhydrous DMSO at room temperature for between 1 hour and 2.5 hours. Next, the aforementioned CsI solution is added to a solution of PbI 2 , PbCl 2 , and anhydrous DMF solvent to form a 1.28 M Pb 2+  solution in which the ratios of Cs to Pb is 1:10 and the ratio of Ito Cl is 9:1. In a particular embodiment, the 1.28 M Pb 2+  solution may be prepared by adding the CsI solution into a vessel containing 1.26 mmol of PbI 2 , 0.14 mmol of PbCl 2 , and 1.0 mL of anhydrous DMF solvent for each 93.8 μL of the CsI solution. The Pb 2+  solution is mixed at a temperature between 50° C. and 100° C. for between 1.5 hour and 2.5 hours before being cooled to form the lead iodide precursor ink. In a particular embodiment, the Pb 2+  solution may be stirred at 85° C. for two hours before being cooled by stirring the solution in a room temperature environment for one hour. In some embodiments, the lead iodide precursor ink may be filtered prior to deposition of the lead iodide precursor ink. A 0.2 μm filter may be used to filter the lead iodide precursor ink, in a particular embodiment. 
     Formamidinium iodide (FAI) and benzylammonium iodide (BzAI) solutions are prepared by dissolving FAI and BzAI salts in anhydrous isopropanol (IPA) to form a 0.2 M FAI solution and 0.05 M BzAI solution, respectively. In particular embodiments, both the FAI and BzAI solutions may be held at 75° C. during the following coating process. 
     Next, the lead iodide precursor ink is deposited onto a substrate and subsequently annealed to form a lead iodide film. In a particular embodiment, the lead iodide precursor ink held at 45° C. may be blade-coated onto a substrate coated with a nickel oxide (NiO) thin film layer and subsequently annealed at 50° C. for 10 minutes to form the lead iodide film. 
     Next, to form the perovskite material layer, the lead iodide film is first underwashed with one coat of the BzAI solution, followed by three coats of the FAI solution. Following deposition of each of the coats of BzAI solution and FAI solution, the coat is allowed to dry prior to deposition of the following coating. In particular embodiments, both the BzAI and the FAI solutions may be held at 45° C. during deposition of each respective coat. After the third FAI coat has been deposited, the substrate and coatings may be annealed to form the perovskite material layer. In a particular embodiment, after the third FAI has been deposited, the substrate is immediately heated to 157° C. for 5 minutes to anneal the perovskite material layer. 
     The foregoing method may have several advantages. For example, depositing the BzAI solution onto the lead iodide film prior to deposition of the FAI solution may provide intermediate templating for growth of the 3D FAPbI 3  perovskite material by formation of a 2D perovskite material. BzAI may react with lead iodide thin film to form an intermediate 2D perovskite material phase. Upon reacting with FAI after deposition of the FAI solution, the BzA +  cations in the 2D phase may be fully or partially replaced with FA +  cations to form a 3D FAPbI 3  framework. Additionally, the BzAI may also passivate crystal defects in the 3D FAPbI 3  perovskite material. Photoluminescence intensity of FAPbI 3  thin films formed by the process described above is brighter (higher) compared to that of FAbI 3  thin films formed by a process not including BzAI.  FIG.  31    illustrates both optical (absorbance) and photoluminescence images of a perovskite material photovoltaic device  3105  produced without addition of BzAI and perovskite material photovoltaic device  3110  produced with BzAI as described herein.  FIG.  31    shows that the optical image of perovskite material photovoltaic device  3110  is darker, indicating a higher light absorbance, and the photoluminescence image of perovskite material photovoltaic device  3110  is brighter than perovskite material photovoltaic device  3105 . Additionally, power output has been observed to be greater from perovskite material photovoltaic devices incorporating BzAI.  FIG.  32    illustrates power output curve  3205  corresponding to a photovoltaic device without BzAI, such as photovoltaic device  3105 , and power output curve  3210  corresponding to a photovoltaic device with BzAI as described herein, such as photovoltaic device  3110 . The power output measurements depicted in  FIG.  32    were measured at maximum power point under 100 mW/cm 2  AM1.5G illumination for 180 seconds with an intervening 30 second dark measurement to demonstrate steady-state performance. As can be seen from  FIG.  32   , a photovoltaic device incorporating BzAI during production produces more power per unit area (16.0 mW/cm 2 ) more voltage (785 mV), and more current per unit area (20.3 mA/cm 2 ) than a photovoltaic device produced without BzAI (15.0 mW/cm 2 , 770 mV, and 19.5 mA/cm 2 ).  FIG.  33    illustrates a current-voltage (I-V) scan  3320  of a perovskite material photovoltaic device produced without BzAI, labeled as the sample “5r” line, and a perovskite material photovoltaic device produced with BzAI, labeled as the sample “10r” line. As can be seen from  FIG.  33   , the perovskite material photovoltaic device produced with BzAI produces a greater current across a range of bias voltages than does the perovskite material photovoltaic device produced without BzAI. Additionally,  FIG.  34    shows box plots for open-circuit voltage (Voc), short-circuit current density (Jsc), Fill Factor (FF) and power conversion efficiency (PCE) for six perovskite material photovoltaic devices produced without BzAI (sample 5, r=reverse scan, f=forward scan, and s=steady-state measurement) and six perovskite material photovoltaic devices produced with BzAI (sample 10).  FIG.  35    illustrates external quantum efficiency (EQE) of six perovskite material photovoltaic devices produced without BzAI (plot  3505 ) and six perovskite material photovoltaic devices produced with BzAI (plot  3510 ). Each EQE curve of  FIG.  35    has been integrated to estimate Jsc in mA/cm 2 , illustrating that the perovskite material devices produced with BzAI display a higher Jsc (area under the EQE curve) than the perovskite material devices produced without BzAI. Finally,  FIG.  36    shows an admittance spectroscopy plot  3605  for perovskite material photovoltaic devices produced without BzAI and an admittance spectroscopy plot  3610  for perovskite material photovoltaic devices produced with BzAI. Admittance spectroscopy plot  3610  shows suppressed ion migration for sample devices including benzylammonium when compared to admittance spectroscopy plot  3605  for sample devices not including benzylammonium. Excessive ion migration is known to have deleterious effects on perovskite material device performance and durability, indicating that the inclusion of benzylammonium in perovskite material photovoltaic devices may increase device performance and durability. 
     Diammonium Butane Cation Enhanced Perovskite 
     Incorporation of 1,4-diammonium butane, or other poly-ammonium organic compounds as described below, into the crystal structure of a perovskite material may improve the properties of that material. In one embodiment, addition of 1,4-diammonium butane into a FAPbI 3  perovskite as described below may provide the perovskite material with advantageous properties. In some embodiments, 1,4-diammonium butane may be incorporated into a perovskite material utilizing a 1,4-diammonium butane salt in the place of the bulky organic cation salt in the process described above, and the addition of the 1,4-diammonium butane salt (or other organic polyammonium salt described herein) may occur at any stage of the perovskite production method for which addition of the bulky organic cation salt is described above. The inclusion of organic cations, such as 1,4-diammonium butane, into the crystal structure of a perovskite material may result in the formula of the perovskite material deviating from the “ideal” stoichiometry of perovskite materials disclosed herein. For example, inclusion of such organic cations may cause the perovskite material to have a formula that is either substoichiometric or superstoichiometric with respect to the FAPbI 3  formula. In this case, the general formula for the perovskite material may be expressed as C x M y X z , where x, y and z are real numbers. 
     In one embodiment, a 1,4-diammonium butane salt solution may be added to the lead halide precursor ink solution prior to deposition. In certain embodiments, a 1,4-diammonium butane salt may be added to the lead halide precursor ink solution at a concentration of 0.001 mol % to 50 mol %. In some embodiments, the 1,4-diammonium butane salt may be added to the lead halide precursor ink solution at a concentration of 0.1 mol % to 20 mol %. In particular embodiments, the 1,4-diammonium butane salt may be added to the lead halide precursor ink solution at a concentration of 1 mol % to 10 mol %. 
     In another embodiment, 1,4-diammonium butane salt may be added to the formamidinium salt solution prior to contacting the formamidinium salt solution with the lead halide precursor thin film as described above. In certain embodiments, a 1,4-diammonium butane salt may be added to the formamidinium iodide salt solution at a concentration of 0.001 mol % to 50 mol %. In some embodiments, the 1,4-diammonium butane salt may be added to the formamidinium iodide salt solution at a concentration of 0.1 mol % to 20 mol %. In particular embodiments, the 1,4-diammonium butane salt may be added to the formamidinium iodide salt solution at a concentration of 1 mol % to 10 mol %. 
     In other embodiments, a 1,4-diammonium butane salt precursor solution may be deposited onto a lead halide thin film formed after deposition of a lead halide precursor ink or onto a perovskite precursor thin film after deposition of the formamidinium salt solution. In certain embodiments, the 1,4-diammonium butane salt precursor solution may have a concentration of 0.001 mol % to 50 mol %. In some embodiments, the 1,4-diammonium butane salt precursor solution may have a concentration of 0.1 mol % to 20 mol %. In particular embodiments, the 1,4-diammonium butane salt precursor solution may have a concentration of 1 mol % to 10 mol %. 
     An example method for depositing a perovskite material including 1,4-diammonium butane includes depositing a lead salt precursor onto a substrate to form a lead salt thin film and depositing an organic cation salt precursor comprising a first organic cation salt onto the lead salt thin film to form a perovskite precursor thin film. The lead salt precursor or the organic cation salt precursor may include a 1,4-diammonium butane salt or a 1,4-diammonium butane salt precursor may be deposited onto the lead salt thin film or the perovskite precursor thin film. Finally the substrate and perovskite precursor thin film may be annealed to form a perovskite material that includes 1,4-diammonium butane. The lead salt precursor and organic cation salt precursor may include any solutions described herein used to produce a perovskite thin film. 
     1,4-diammonium butane has nearly the same length between its ammonium groups as occurs between formamidinium cations in the formamidinium lead iodide perovskite material crystal lattice. Accordingly, the 1,4-diammonium butane may substitute for two formamidinium ions during the formation of an FAPbI 3  material. In alternate embodiments, other alkyl polyammonium salts may be added to the lead halide precursor ink during formation of the perovskite material. For example, 1,8 diammonium octane, bis(4-aminobutyl)amine, and tris(4-aminobutyl)amine may be added. Additionally, the polyammonium polycations, including 1,4-diammonium butane, may provide the same benefits as the bulky organic cations described above by similar mechanisms to those described above with respect to the bulky organic cations. 
       FIG.  13    is a stylized illustration of an effect of addition of a 1,4-diammonium butane salt during the process of producing a perovskite material may have on the resulting perovskite  7000 . As illustrated by  FIG.  13   , the 1,4-diammonium butane cation  7020  may substitute for two formamidinium cations  7010  in the perovskite material crystal lattice. In FAPbI 3  perovskite, the spacing between formamidinium cations is approximately 6.35 Å. The length of the length of the 1,4-diammonium butane cation is approximately 6.28 Å, a difference of only 0.07 Å. Accordingly, the 1,4-diammonium butane cation may substitute into the perovskite crystal lattice without significantly changing the properties or structure of the perovskite crystal lattice. In some embodiments, the addition of the 1,4-diammonium butane cation to a perovskite material may enhance the properties and stability of the perovskite material. The 1,4-diammonium butane cation may act as a rigid structure within the perovskite material, increasing its structural and chemical durability. For example, in some embodiments perovskite material with added 1,4-diammonium butane cation may demonstrate superior dry heat stability compared to a perovskite material without 1,4-diammonium butane cation. Additionally, a perovskite material with added 1,4-diammonium butane cation may demonstrate a blue shift in the emission spectra of the perovskite material. In some embodiments the 1,4-diammonium butane cation may be added at a concentration between 0 and 20 mol % to the formamidinium salt solution. In other embodiments the 1,4-diammonium butane cation may be added at a concentration between 1 and 5 mol % to the formamidinium salt solution. In a particular embodiment the 1,4-diammonium butane cation added at a concentration 5 mol % to the formamidinium salt solution. 
     Experimental evidence has shown that for additions of up to 20% 1,4-diammonium butane to a perovskite material, the lattice parameters do not appreciably shift.  FIG.  14    provides x-ray diffraction peaks (XRD) for perovskite having 0 mol %, 5 mol %, 10 mol %, and 20 mol % 1,4-diammonium butane (“DABI”). For each concentration the major peaks occur at the same points, indicating that the lattice parameters for a perovskite material do not change appreciably with addition of a concentration between 0 mol % and 20 mol % 1,4-diammonium butane. The addition of 1,4-diammonium butane may create small intensity diffractions at less than 13° 20 with Cu-Kα radiation, which are indicative of a small amount of 2D or layered perovskite phase. 
       FIG.  15    provides images of perovskite samples having 0 mol %, 1 mol %, 2.5 mol % and 5 mol % exposed to a temperature of 85° C. at 0% relative humidity for seven days. The perovskite material with 0 mol % DABI shows significant lightening in color after one day and even more significant yellowing after seven days. This indicates that the perovskite material with 0 mol % DABI has degraded significantly after one day exposed to the testing conditions. The perovskite material samples with 1 mol %, 2.5 mol % and 5 mol % all remain dark after seven days, indicating that addition of as little as 1 mol % DABI significantly increases so called “dry heat” stability of the perovskite material. 
     Additionally, addition of 1,4-diammonium butane to a perovskite material may result in a slight blue shift of photoluminescence seen from a perovskite material when compared to a perovskite material without 1,4-diammonium butane. This blue shift results from the passivation of trap states within the perovskite material resulting from the addition of 1,4-diammonium butane. This blue shift indicates that the addition of 1,4-diammonium butane to a perovskite material decreases defect density in the perovskite material crystal lattice without changing the crystal structure of the perovskite material. For example, it has been observed that the resulting blue shift seen in an FAPbI 3  perovskite material with 20 mol % of added 1,4-diammonium butane compared to a FAPbI 3  perovskite material without 1,4-diammonium butane is a change of 0.014 eV, from 1.538 eV with no 1,4-diammonium butane to 1.552 eV with 20 mol % 1,4-diammonium butane. 
     In other embodiments, other ammonium complexes may be added during formation of the perovskite material. For example,  FIG.  16    illustrates three ammonium compounds, 1,8-diammonium octane, bis(4-aminobutyl)-ammonium and tris(4-aminobutyl)-ammonium, which may be added to a perovskite material in the same method as described above with respect to the 1,4-diammonium butane cation. 1,8-diammonium octane may occupy the space of two formamidinium cations (“A-sites”) of a FAPbI 3  perovskite material crystal lattice when introduced during the formation of the perovskite material as described above. Bis(4-aminobutyl)-ammonium may occupy the space of three A-sites of a FAPbI 3  perovskite material crystal lattice when introduced during the formation of the perovskite material as described above. Tris(4-aminobutyl)-ammonium may occupy the space of four A-sites of a FAPbI 3  perovskite material crystal lattice when introduced during the formation of the perovskite material as described above.  FIGS.  16 A-C  provides a stylized illustration of an incorporation into FAPbI 3  perovskite material crystal lattice of the three ammonium compounds illustrated in  FIG.  16   .  FIG.  16 A  is a stylized illustration incorporation of 1,8-diammonium octane into a FAPbI 3  perovskite material crystal lattice  7100 . As illustrated by  FIG.  16 A , the 1,8-diammonium octane cation  7120  may substitute for two formamidinium cations  7110  in the perovskite material crystal lattice.  FIG.  16 B  is a stylized illustration incorporation of bis(4-aminobutyl)-ammonium into a FAPbI 3  perovskite material crystal lattice  7200 . As illustrated by  FIG.  16 B , the bis(4-aminobutyl)-ammonium cation  7220  may substitute for three formamidinium cations  7210  in the perovskite material crystal lattice.  FIG.  16 C  is a stylized illustration incorporation of tris(4-aminobutyl)-ammonium into a FAPbI 3  perovskite material crystal lattice  7300 . As illustrated by  FIG.  16   c   , the tris(4-aminobutyl)-ammonium cation  7320  may substitute for four formamidinium cations  7310  in the perovskite material crystal lattice. In other embodiments, alkyl diammonium complexes with carbon chains between 2 and 20 carbon atoms may be added to a perovskite material. In some embodiments, a combination of ammonium complexes may be added to a perovskite material. 
     Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood as referring to the power set (the set of all subsets) of the respective range of values, and set forth every range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee.