Patent Publication Number: US-11659723-B2

Title: Perovskite material photovoltaic device and method for assembly

Description:
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. Solution processing of thin-film PVs provides an economical method for depositing the various layers which make up PVs. However, the various solution processes needed to deposit each layer may not be compatible with prior deposited layers. Therefore, a method for assembling PV devices is needed to produce PV devices with adjacent layers deposited by incompatible solution chemistry. 
     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 
     A method for manufacturing a photovoltaic device, according to some embodiments, includes the steps of: fabricating a first photovoltaic device portion with a first perovskite material layer having a first face, fabricating a second photovoltaic device portion with a second perovskite material layer having a second face, arranging the first photovoltaic device portion and the second photovoltaic device portion such that the first face is in contact with the second face, and compressing the first photovoltaic device portion and second photovoltaic device portion at a pressure sufficient to fuse the first perovskite material to the second perovskite material. 
     In particular embodiments, the method includes sealing the photovoltaic device. 
     In particular embodiments, the method includes placing a glass frit along a perimeter of first photovoltaic device portion prior to compressing the first photovoltaic device portion and second photovoltaic device portion. 
     In particular embodiments, the first photovoltaic device portion further includes a first substrate, a first electrode layer deposited onto the first substrate, a first interfacial layer deposited between the first electrode layer and the first perovskite material layer. The second photovoltaic device portion further includes a second substrate, a second electrode layer deposited onto the second substrate, a second interfacial layer deposited between the second electrode layer and the second perovskite material layer. 
     In particular embodiments, the first perovskite material layer and the second perovskite material layer have the same chemical formula and composition. 
     In particular embodiments, the first perovskite material layer and second perovskite material layer comprise a formamidinium lead iodide perovskite material. 
     In particular embodiments, the first perovskite material layer comprises a perovskite material having the formula FAPbI 3  and the second perovskite material layer comprises a perovskite having the formula MAPbI 3 . 
     In particular embodiments, the first perovskite material layer comprises a perovskite material having the formula CsPbI 3  and the second perovskite material layer comprises a perovskite having the formula FAPbI 3 . 
     In particular embodiments, the first perovskite material layer comprises a perovskite material having the formula FASnI 3  and the second perovskite material layer comprises a perovskite having the formula FAPbI 3 . 
     In particular embodiments, the pressure sufficient to fuse the first perovskite material to the second perovskite material is between 1 and 7 MPa. 
     In particular embodiments, the method includes heating the first photovoltaic device portion and second photovoltaic device portion to a temperature between 75° C. and 177° C. while first photovoltaic device portion and second photovoltaic device portion are being compressed. 
     In particular embodiments, the method includes heating the first photovoltaic device portion and second photovoltaic device portion to a temperature between 75° C. and 177° C. while first photovoltaic device portion and second photovoltaic device portion are being compressed, and wherein the pressure sufficient to fuse the first perovskite material to the second perovskite material is between 1 and 7 MPa. 
     In particular embodiments, the method includes depositing a glass frit paste, ink, solution, or powder around a perimeter of the first photovoltaic device portion prior to compressing the first photovoltaic device portion and second photovoltaic device portion. 
     According to some embodiments, a method for manufacturing an electronic device includes depositing a first electrode layer onto a first substrate, depositing one or more first interfacial layers onto the first electrode layer, depositing a first perovskite material layer onto the one or more first interfacial layers, depositing a second electrode layer onto a second substrate, depositing one or more second interfacial layers onto the second electrode layer, depositing a second perovskite material layer onto the one or more second interfacial layers, orienting the second substrate such that the second perovskite material layer is in contact with the first perovskite material layer, and applying a sufficient pressure to the second substrate to fuse the second perovskite material layer with the first perovskite material layer. 
     In particular embodiments, the first perovskite material layer and the second perovskite material layer have the same chemical formula and composition. 
     In particular embodiments, the first perovskite material layer and second perovskite material layer comprise a formamidinium lead iodide perovskite material. 
     In particular embodiments, the first perovskite material layer comprises a perovskite material having the formula FAPbI 3  and the second perovskite material layer comprises a perovskite having the formula MAPbI 3 . 
     In particular embodiments, the pressure sufficient to fuse the first perovskite material to the second perovskite material is between 1 and 7 MPa. 
     In particular embodiments, the method includes heating the first photovoltaic device portion and second photovoltaic device portion to a temperature between 75° C. and 177° C. while first photovoltaic device portion and second photovoltaic device portion are being compressed. 
     In particular embodiments, the method includes heating the first photovoltaic device portion and second photovoltaic device portion to a temperature between 75° C. and 177° C. while first photovoltaic device portion and second photovoltaic device portion are being compressed, and wherein the pressure sufficient to fuse the first perovskite material to the second perovskite material is between 1 and 7 MPa. 
     In particular embodiments, the method includes depositing a glass frit paste, ink, solution, or powder around a perimeter of the first substrate prior to applying sufficient pressure to the second substrate to fuse the second perovskite material layer with the first perovskite material layer. 
     According to some embodiments, a photovoltaic device includes a first substrate, a second substrate, a perovskite material layer disposed between the first substrate and the second substrate, a first electrode layer in contact with first substrate and disposed between the first substrate and the perovskite material layer, a second electrode layer in contact with the second substrate and disposed between the second substrate and the perovskite material layer, a first interfacial layer disposed between the first electrode layer and the perovskite material layer, a second interfacial layer disposed between the perovskite material layer and the second electrode layer. There is not an encapsulant layer between the first electrode layer and the first substrate and there is not an encapsulant layer between the second electrode layer and the second substrate. 
     In particular embodiments, the perovskite material layer comprises a first perovskite material and a second perovskite material fused together. 
     In particular embodiments, the perovskite material layer comprises formamidinium lead iodide. 
     In particular embodiments, the first perovskite material comprises methylammonium lead iodide. 
     In particular embodiments, the first substrate comprises glass and the second substrate comprises glass. 
     In particular embodiments, the first substrate comprises glass and the second substrate comprises a material that is not glass. 
     In particular embodiments, the first interfacial layer is an electron transport layer and the second interfacial layer is a hole transport layer. 
     In particular embodiments, a sealing structure disposed between the first substrate and the second substrate. The sealing structure is fused to the first substrate and second substrate and is arranged such that the perovskite material layer, first electrode layer, second electrode layer, first interfacial layer, second interfacial layer are sealed interior to the first substrate, second substrate, and sealing structure. 
     In particular embodiments, the sealing structure comprises glass. 
     Advantages of the present invention may include enabling assembly of thin film PV devices with adjacent layers produced with incompatible solution chemistry. In particular, perovskite layers may be sensitive to many of the solvents used in solution-based methods for deposition of interfacial layers. The present invention provides a method of assembly for PV devices that enables a perovskite material layer to be placed adjacent to an interfacial layer deposited with solution chemistry that would otherwise damage the perovskite material layers. Additionally, in traditional “bottom-up” manufacturing of a thin-film PV device, a sealing or encapsulant layer is required to be deposited on top of the “top” electrode prior to fitment of the “top” substrate/superstrate. The techniques described herein provide a method for constructing two portions of a PV device using bottom up method and then assembling those portions such that an encapsulant layer is not required prior to fitment of the “top” substrate/superstrate. 
    
    
     
       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 a method for assembly of an example device according to some embodiments of the present disclosure. 
         FIG.  6    is a stylized diagram showing a method for assembly of an example device according to some embodiments of the present disclosure. 
         FIG.  7    is a stylized diagram showing a method for assembly an example device according to some embodiments of the present disclosure. 
         FIG.  8    is a stylized diagram showing a method for assembly an example device according to some embodiments of the present disclosure. 
         FIG.  9    is a stylized diagram showing a method for assembly an example device according to some embodiments of the present disclosure. 
         FIG.  10    is a stylized diagram showing a method for assembly an example device according to some embodiments of the present disclosure. 
         FIG.  11    is a stylized diagram showing a method for assembly an example device according to some embodiments of the present disclosure. 
         FIG.  12    is a stylized diagram showing a method for sealing an example device according to some embodiments of the present disclosure. 
         FIG.  13    is a stylized diagram showing a method for assembly an example device according to some embodiments of the present disclosure. 
         FIG.  14    is a stylized diagram showing a method for assembly an example device according to some embodiments of the present disclosure. 
         FIG.  15    provides a stylized illustration of thicknesses of inorganic metal halide sublattices of perovskite materials according to some embodiments of the present disclosure. 
         FIG.  16    is a stylized diagram of 2-terminal photovoltaic cell according to some embodiments of the present disclosure. 
         FIG.  17    is a stylized diagram of 3-terminal photovoltaic cell according to some embodiments of the present disclosure. 
         FIG.  18    is a stylized diagram of 4-terminal photovoltaic cell according to some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     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. 
     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 w 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 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.  15   , the n-value indicates the thickness of an inorganic metal halide sublattice  1300  of the perovskite material. 
     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, 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. 
     In certain embodiments, C may include a formamidinium (FA), 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, 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., 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, 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., octahydropyrimido[1,2-a]pyrimidine, pyrimido[1,2-a]pyrimidine, hexahydroimidazo[1,2-a]-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, 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. 
     
       
         
         
             
             
         
       
     
     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, triflate, tetrafluoroborate, hexafluorophosphate, tetrakis [3,5-bis (trifluoromethyl) phenyl]borate (“BARF”), 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 CM 2 X 7  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 C 2 MX 4  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 . 
     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 resulting conversion of PbI 2  to MAPbI 3  may be 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 ). Tandem PVs may include “2-terminal” tandem cells, “3-terminal” tandem cells, and “4-terminal” tandem cells. In a 2-terminal tandem cell, a PV cell, such as device  3900 , may be connected to electrical leads by electrodes near the edges of the PV cell, such as electrodes  3912  and  3902 . In a 3-terminal tandem device, the PV cell may be connected to electrical leads by two electrodes near the edges of the PV cell, such as electrodes  3912  and  3902 , and by a third electrode disposed within the interior of the cell between the two photoactive layers, such as an electrode disposed in layer  3907 . In a 4-terminal cell, a PV cell may be connected to electrical leads by two electrodes near the edges of the PV cell, such as electrodes  3912  and  3902 , and by two electrodes that are separated by a transparent, non-conductive layer and are disposed within the interior of the PV cell between the two photoactive layers. For example, in a 4-terminal device, layer  3907  may include, among other layers, two electrodes separated by a transparent, non-conductive layer, such as glass. Stylized illustrations of a 2-terminal tandem cell, a 3-terminal tandem cell, and a 4-terminal tandem cell are illustrated in  FIGS.  16 ,  17 , and  18   , respectively. 
       FIG.  16    illustrates a 2-terminal tandem PV cell  6000 . PV cell  6000  includes two electrically conductive electrode layers, a first electrode layer  6021  and a second electrode layer  6022 . Electrode layers  6021  and  6022  may be transparent conductors such as tin-doped indium oxide (ITO) or any other material as described herein. In other embodiments, electrode layers  6021  and  6022  may be a metal, such as aluminum, or other conducive material such as carbon. PV cell  6000  also includes interfacial layers (IFL)  6031 ,  6032 , and  6033 . IFLs  6031 ,  6032 , and  6033  may assist in charge recombination. In some embodiments, each IFL layer may be a multi-layer IFL. An IFL may be intrinsic, ambipolar, p-type, or n-type semiconducting materials or may be a dielectric material. PV cell  6000  may be attached to electrical leads by electrodes  6021  and  6022 , which may connect PV cell  6000  to a discharge unit, such as a battery, motor, capacitor, electric grid, or any other electrical load. 
       FIG.  17    illustrates a 3-terminal PV cell  7000 . PV cell  7000  may be attached to electrical leads by electrode  7021 , an electrode  7022  embedded within IFLs  7032  and  7033 , and electrode  7023 . In some embodiments, electrode layers  7021  and  7023  may be cathodes and electrode layer  7022  may be an anode. In other embodiments, electrode layers  7021  and  7023  may be anodes and electrode layer  7022  may be a cathode. As with PV cell  6000  illustrated in  FIG.  16   , IFLs  7031 ,  7032 ,  7033 , and  7034  may be single or multi-layer IFLs and may be intrinsic, ambipolar, p-type, or n-type semiconducting materials or may be a dielectric material. In embodiments in which electrode layer  7022  is a cathode, IFLs  7032  and  7033  may be electron transporting layers (n-type layers). In embodiments in which electrode layer  7022  is an anode, IFLs  7032  and  7033  may be hole transporting layers (p-type). In some embodiments, one or more of IFLs  7031 ,  7032 ,  7033 , or  7034  may be omitted from PV cell  7000 . 
       FIG.  18    illustrates a 4-terminal PV cell  8000 . PV cell  8000  may be attached to electrical leads by electrode layers  8021 ,  8022 ,  8023 , and  8024 . In some embodiments, electrode layer  8021  may be an anode and electrode layer  8022  may be a cathode, and electrode layer  8024  may be an anode and electrode layer  8023  may be a cathode. In other embodiments, electrode layer  8021  may be an anode and electrode layer  8022  may be a cathode, and electrode layer  8024  may be a cathode and electrode layer  8023  may be an anode. In other embodiments, electrode layer  8021  may be a cathode and electrode layer  8022  may be anode, and electrode layer  8024  may be a cathode and electrode layer  8023  may be an anode. In other embodiments, electrode layer  8021  may be a cathode and electrode layer  8022  may be anode, and electrode layer  8024  may be an anode and electrode layer  8023  may be a cathode. A 4-terminal design tandem solar cell device may, in some embodiments, include two devices made up of monolithically stacked layers. The two devices may be joined using a layer of adhesive, epoxy, glass, laminate, or any combination thereof. For example, with reference to  FIG.  18   , a first device may include substrate  8011 , electrode layer  8021 , IFL  8031 , photoactive layer  8041 , IFL  8032 , and electrode layer  8022 , and a second device may include substrate  8012 , electrode layer  8024 , IFL  8034 , photoactive layer  8042 , IFL  8033 , and electrode layer  8023 . These devices may be joined by transparent, non-conductive layer  8051 , which may be an adhesive, epoxy, glass, laminate, or combination thereof. 
     As with PV cell  6000  and PV cell  7000  illustrated in  FIGS.  16  and  17   , IFLs  8031 ,  8032 ,  8033 , and  8034  may be single or multi-layer IFLs and may be intrinsic, ambipolar, p-type, or n-type semiconducting materials or may be a dielectric material. In embodiments in which electrode layer  8022  and/or electrode layer  8023  is a cathode, IFL  8032  and/or IFL  8033  may be electron transporting layers (n-type layers). In embodiments in which electrode layer  8022  and/or electrode layer  8023  is an anode, IFL  8032  and/or IFL  8033  may be hole transporting layers (p-type). In some embodiments, one or more of IFLs  8031 ,  8032 ,  8033 , or  8034  may be omitted from PV cell  8000 . Non-conductive layer  8051 , may be any transparent material that does not conduct electricity between electrode layer  8022  and electrode layer  8023 . For example, non-conductive layer  8051  may be glass, quartz, sapphire, silicon carbide, or a transparent polymer such as polycarbonate or poly(methyl methacrylate) (PMMA). In some embodiments, transparent non-conductive layer  8051  may be assembled from two transparent non-conductive layers fused through application of pressure and/or temperature as described here. In such embodiments, transparent non-conductive layer  8051  may include a thin polymer or adhesive layer placed between the layers prior to fusing. 
     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, N3, 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   . 
     Method for Manufacturing Perovskite Material Devices 
       FIG.  5    is a stylized diagram of a method for assembling an example photovoltaic device  330 , according to certain embodiments. First, a first photovoltaic device portion  310  with a first perovskite material layer  311  having a face  316  is fabricated. Next, a second photovoltaic device portion  321  with a second perovskite material layer  321  having a face  326  is fabricated. Next, the first photovoltaic device portion  310  and the second photovoltaic device portion  320  are arranged such that the face  316  of the first perovskite material layer  311  is in contact with the face  326  of the second perovskite material layer  321 . Next, the first photovoltaic device portion  310  and second photovoltaic device portion  320  are compressed and heated to a pressure and temperature sufficient to fuse the first perovskite material layer  311  to the second perovskite material layer  321 . The resulting photovoltaic device  330  has a single perovskite material layer  331 . 
     In some embodiments, photovoltaic device portion  310  may include a substrate  312 , electrode layer  313 , and one or more interfacial layers  314  in addition to the perovskite material layer  311 . In some embodiments, photovoltaic device portion  320  may include a substrate  322 , electrode layer  323 , and one or more interfacial layers  324  in addition to the perovskite material layer  321 . Each of the one or more interfacial layers  314  and  324  may include any material described herein as an interfacial layer. Each of the electrode layers  312  and  322  may include any electrode material described herein, including for example, indium tin oxide (ITO) and fluorine doped tin oxide (FTO). 
     Photovoltaic device portion  310 , in some embodiments, may be constructed by depositing an electrode layer  313  onto a substrate  312 , then depositing one or more interfacial layers  314  onto electrode layer  313 , and finally depositing a perovskite material layer  311  onto the one or more interfacial layers  314 . Photovoltaic device portion  320 , in some embodiments, may be constructed by depositing an electrode layer  323  onto a substrate  322 , then depositing one or more interfacial layers  324  onto electrode layer  323 , and finally depositing a perovskite material layer  321  onto the one or more interfacial layers  324 . Any process for depositing a thin film layer described herein may be used to deposit the electrode layers  313  and  323 , interfacial layers  314  and  324 , and perovskite material layers  311  and  321 . 
     Perovskite material layers  311  and  321  may be a perovskite material described herein. In some embodiments, perovskite material layers  311  and  321  may be the same perovskite material. For example, perovskite material layers  311  and  321  may both include a formamidinium lead iodide (FAPbI 3 ) perovskite material. In other embodiments, perovskite material layers  311  and  321  may each include a different perovskite material than the other. For example, perovskite material layer  311  may comprise a perovskite material having the formula FAPbI 3  and perovskite material layer  321  may comprise a perovskite material having the formula MAPbI 3 . In another embodiment, perovskite material layer  311  may comprise a perovskite material having the formula CsPbI 3  and perovskite material layer  321  may comprise a perovskite material having the formula FAPbI 3 . In yet another embodiment, perovskite material layer  311  may comprise a perovskite material having the formula FASnI 3  and perovskite material layer  321  may comprise a perovskite material having the formula FAPbI 3 . Using different perovskite materials for perovskite material layers  311  and  321  may result in a perovskite material layer  331  having a gradient of optical absorption characteristics, absorbing certain wavelengths at some depths and different wave lengths at greater depths. Such a gradient may result in enhanced efficiency for photovoltaic device  330  through implementation of a perovskite material layer  331  with a broader absorption spectrum than could be achieved using a single perovskite material. 
     The pressure applied to photovoltaic device portions  310  and  320  may range between 0.1 and 30 MPa and may be applied for between 1 second and 100 minutes. In certain embodiments, the pressure applied to photovoltaic device portions  310  and  320  may range from 1 to 7 MPa and may be applied for 5 to 45 minutes. Pressure may be applied to photovoltaic device portions  310  and  320  by any means capable of applying a compressive force to photovoltaic device portions  310  and  320 . For example, hydraulic presses, pneumatic presses, screw driven mechanical presses or clamps, gear driven mechanical presses or clamps, or weights, may be used to apply pressure to photovoltaic device portions  310  and  320 . 
     While pressure is applied to photovoltaic device portions  310  and  320 , photovoltaic device portions  310  and  320  may be head to and held at an elevated temperature. In some embodiments, the temperature of photovoltaic device portions  310  and  320  may be increased prior to the application of pressure. In other embodiments, the temperature of photovoltaic device portions  310  and  320  may be increased during the application of pressure. The temperature of photovoltaic device portions  310  and  320  may be increased to a temperature between 20° and 500° Celsius prior to or during the application of pressure to photovoltaic device portions  310  and  320 . In particular embodiments, the temperature of photovoltaic device portions  310  and  320  may be increased to a temperature between 75° and 177° Celsius prior to or during the application of pressure to photovoltaic device portions  310  and  320 . 
     Assembling a photovoltaic device as illustrated by  FIG.  5    provides several advantages to prior “bottom-up” methods of assembly for thin film devices, wherein each subsequent layer was deposited on top of the preceding layers. One advantage of the method illustrated in  FIG.  5    is that it enables construction of a photovoltaic device with interfacial layers above and below the perovskite material layer  331  that may require deposition methods that would be detrimental to perovskite layer  331 . Previously, after a perovskite material layer was deposited onto such an interfacial layer, another such interfacial layer could not be deposited on top of the perovskite material layer without degrading the perovskite material layer. This resulted in compromises in choice of interfacial layers, which could lead to sub-optimal photovoltaic device performance. The method illustrated by  FIG.  5   , and the variations on that method described herein with respect to  FIGS.  6 - 10   , allow for assembly of a photovoltaic device without the need to deposit an interfacial layer on top of a perovskite material layer, thereby enabling optimized selection of interfacial layers. For example, many interfacial layers are preferably deposited using techniques such as sputtering or electron beam deposition and are annealed at temperatures greater than 150° C., which may damage the perovskite material layer. By enabling construction of photovoltaic devices with interfacial layers that are deposited before the perovskite material layer, the method illustrated by  FIG.  5    allowed for deposition of interfacial layers by the preferred methods. Additionally, the techniques described herein enable construction of a photovoltaic device without use of an encapsulation layer between the electrode layer and the “top” substrate, because each electrode layer is deposited directly onto the substrate prior to assembly of the photovoltaic device. 
       FIG.  6    illustrates a particular embodiment of the method for assembling a photovoltaic device as described with respect to  FIG.  5   . In the embodiment illustrated in  FIG.  6   , photovoltaic device portion  410  includes a glass layer  412 , fluorine doped tine oxide layer  413 , electron transport layer  414 , and perovskite material layer  411 . Photovoltaic device portion  420 , in the embodiment illustrated in  FIG.  6   , includes a glass layer  422 , indium tin oxide layer  423 , hole transport layer  424 , and perovskite material layer  421 . 
       FIG.  7    illustrates a particular embodiment of the method for assembling a photovoltaic device as described with respect to  FIG.  5   . In the embodiment illustrated in  FIG.  7   , photovoltaic device portion  510  includes a substrate layer  512 , metallic electrode layer  513 , electron transport layer  514 , and perovskite material layer  511 . In some embodiments, for example, in high-power applications such as power plants, substrate layer  512  may be non-transparent. In other embodiments, for example in lower-power applications such as solar windows, substrate layer  512  may be transparent or translucent. Photovoltaic device portion  520 , in the embodiment illustrated in  FIG.  7   , includes a glass layer  522 , indium tin oxide layer  523 , hole transport layer  524 , and perovskite material layer  521 . 
       FIG.  8    illustrates a particular embodiment of the method for assembling a photovoltaic device as described with respect to  FIG.  5   . In the embodiment illustrated in  FIG.  8   , photovoltaic device portion  610  includes a glass layer  612 , fluorine doped tine oxide layer  613 , electron transport layer  614 , and perovskite material layer  611 . Photovoltaic device portion  620 , in the embodiment illustrated in  FIG.  8   , includes a substrate layer  622 , metallic electrode layer  623 , hole transport layer  624 , and perovskite material layer  621 . In some embodiments, for example, in high-power applications such as power plants, substrate layer  622  may be non-transparent. In other embodiments, for example in lower-power applications such as solar windows, substrate layer  622  may be transparent or translucent. 
       FIG.  9    illustrates a particular embodiment of the method for assembling a photovoltaic device as described with respect to  FIG.  5   . In the embodiment illustrated in  FIG.  9   , photovoltaic device portion  710  includes a glass layer  712 , fluorine doped tine oxide layer  713 , and electron transport layer  714 . Photovoltaic device portion  720 , in the embodiment illustrated in  FIG.  9   , includes a glass layer  722 , indium tin oxide layer  723 , hole transport layer  724 , and perovskite material layer  721 . In the embodiment illustrated in  FIG.  9   , only as single perovskite material layer  721  is present in photovoltaic device portion  720 , and no perovskite material layer is present in photovoltaic device portion  710 . When the photovoltaic device portions are compressed and annealed, perovskite material layer  721  fuses to electron transport layer  714 , resulting in photovoltaic device  730 . 
       FIG.  10    illustrates a particular embodiment of the method for assembling a photovoltaic device as described with respect to  FIG.  5   . In the embodiment illustrated in  FIG.  10   , photovoltaic device portion  810  includes a glass layer  812 , fluorine doped tine oxide layer  813 , and electron transport layer  814 , perovskite material layer  811 . Photovoltaic device portion  820 , in the embodiment illustrated in  FIG.  10   , includes a glass layer  822 , indium tin oxide layer  823 , and hole transport layer  824 . In the embodiment illustrated in  FIG.  10   , only as single perovskite material layer  811  is present in photovoltaic device portion  810 , and no perovskite material layer is present in photovoltaic device portion  720 . When the photovoltaic device portions are compressed and annealed, perovskite material layer  811  fuses to hole transport layer  824 , resulting in photovoltaic device  830 . 
       FIG.  11    illustrates a particular embodiment of the method for assembling a photovoltaic device as described with respect to  FIG.  5   . The embodiment illustrated in  FIG.  11   , shows a method for assembling a tandem photovoltaic device that has two perovskite material layers and one or more interfacial layers between the perovskite material layers. These one or more interfacial layers between the perovskite material layers may be referred to as a recombination layer. In the embodiment illustrated in  FIG.  11   , photovoltaic device portion  910  includes a substrate layer  912 , electrode layer  913 , one or more interfacial layers  914 , perovskite material layer  911 , one or more interfacial layers  924 , and a perovskite material layer  921 . Photovoltaic device portion  930 , in the embodiment illustrated in  FIG.  11   , includes a substrate layer  932 , electrode layer  933 , one or more interfacial layers  934 , and perovskite material layer  931 . When the photovoltaic device portions are compressed and annealed, perovskite material layer  931  fuses to perovskite layer  921  to form a fused perovskite material layer  941 , resulting in photovoltaic device  940 . In some embodiments, various layers may be omitted. For example, perovskite material  921  may be omitted and perovskite material  931  may be fused directly to IFLs  924 . In certain embodiments, photovoltaic device portion  910  may be assembled in a manner similar to that illustrated in  FIG.  5   , and then additional IFLs  924  and perovskite material layer  921  may be deposited onto the PV cell prior to fusing with photovoltaic device portion  930 . In such an embodiment, a substrate such as substrate  322  of  FIG.  5   , may be removed from the PV cell portion prior to deposition of subsequent layers. 
     Tandem devices including 2-terminal, 3-terminal, and 4-terminal cells discussed herein may be assembled by the methods described with respect to  FIGS.  5 - 11   . For example,  FIG.  11    presents a stylized illustration of an example method for assembling a 2-terminal PV cell according to the present disclosure.  FIG.  13    presents a stylized illustration of an example method for assembling a 3-terminal PV cell, such as PV cell  7000  illustrated in  FIG.  17   , according to the present disclosure. And,  FIG.  14    presents a stylized illustration of an example method for assembling a 4-terminal PV cell, such as PV cell  8000  illustrated in  FIG.  18   , according to the present disclosure. 
     In the embodiment illustrated in  FIG.  13   , photovoltaic device portion  1110  includes a substrate layer  1112 , electrode layer  1113 , one or more interfacial layers  1114 , perovskite material layer  1111 , one or more interfacial layers  1124 , electrode layer  1123 , one or more interfacial layers  1125 , and perovskite material layer  1121 . Photovoltaic device portion  1130 , in the embodiment illustrated in  FIG.  13   , includes a substrate layer  1132 , electrode layer  1133 , one or more interfacial layers  1134 , and perovskite material layer  1131 . When the photovoltaic device portions are compressed and annealed, perovskite material layer  1131  fuses to perovskite layer  1121  to form a fused perovskite material layer  1141 , resulting in photovoltaic device  1140 . It should be understood from the present disclosure that any layer illustrated as being included in photovoltaic device portion  1120  could be included in photovoltaic device portion  1110  prior to compression. For example, in some embodiments, photovoltaic device portion  1110  may include electrode layer  1126  and one or more interfacial layers  1125 . In such an embodiment, interfacial layer  1125  would fuse to perovskite layer  1121  during compression. In some embodiments, various layers may be omitted. For example, perovskite material  1121  may be omitted and perovskite material  1131  may be fused directly to IFLs  1125 . In certain embodiments, photovoltaic device portions  1110  or  1130  may be assembled in a manner similar to that illustrated in  FIG.  5   . 
     In the embodiment illustrated in  FIG.  14   , photovoltaic device portion  1210  includes a substrate layer  1212 , electrode layer  1213 , one or more interfacial layers  1214 , perovskite material layer  1211 , one or more interfacial layers  1224 , electrode layer  1223 , transparent non-conductive layer  1217 , electrode layer  1226 , one or more interfacial layers  1225 , and perovskite material layer  1121 . Photovoltaic device portion  1230 , in the embodiment illustrated in  FIG.  14   , includes a substrate layer  1232 , electrode layer  1233 , one or more interfacial layers  1234 , and perovskite material layer  1231 . When the photovoltaic device portions are compressed and annealed, perovskite material layer  1231  fuses to perovskite layer  1221  to form a fused perovskite material layer  1241 , resulting in photovoltaic device  1240 . It should be understood from the present disclosure that any layer illustrated as being included in photovoltaic device portion  1210  could be included in photovoltaic device portion  1220  prior to compression and vise-versa. For example, in some embodiments, photovoltaic device portion  1230  may omit perovskite material layer  1221 , and include one or more interfacial layers  1225 , electrode layer  1226  and a second transparent non-conductive layer. In such an embodiment, transparent non-conductive layer  1217  would fuse to the second transparent non-conductive material during compression. In some embodiments, photovoltaic device portions  1210  or  1230  may be assembled in a manner similar to that illustrated in  FIG.  5   . 
     In some embodiments, a photovoltaic device assembled as illustrated in  FIGS.  5 - 11 ,  13 , and  14    may be sealed as illustrated in  FIG.  12   . First a glass frit paste, ink, solution, or powder  1050  is placed between glass substrates  1012  and  1022  and around layers  1013 ,  1014 ,  1031 ,  1024 , and  1023 . In some embodiments, the glass frit may be placed onto the substrates of one or both photovoltaic device portions as illustrated in  FIGS.  5 - 11    prior to compression of the two photovoltaic device portions. Next, the glass frit  1050  is heated by a localized heating process such as laser annealing by laser beams  1060 , stir welding, or through compression as described above. Finally, the heated glass frit solidifies to a solid glass  1051  that has bonded to glass substrates  1012  and  1022 , thereby sealing layers  1013 ,  1014 ,  1031 ,  1024 , and  1023  in the interior of the device between glass substrates  1012  and  1022  and solidified glass  1051 . 
     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.