Query: Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskites

Candidate papers:

abstract: Perovskite Photovoltaics For many types of low cost solar cells, including those using dye sensitized titania, performance is limited by low open circuit voltages. Lee et al. (p. 643, published online 4 October; see the Perspective by Norris and Aydil) have developed a solid state cell in which structured films of titania or alumina nanoparticles are solution coated with a lead halide perovskite layer that acts as the absorber and n type photoactive layer. These particles are coated with a spirobifluorene organic hole conductor in a solar cell with transparent oxide and metal contacts. For the alumina particles, power conversion efficiencies of up to 10.9% were obtained. Mesostructured alumina acts as an insulating scaffold for the assembly of very thin films of n and p type semiconductors. The energy costs associated with separating tightly bound excitons (photoinduced electron hole pairs) and extracting free charges from highly disordered low mobility networks represent fundamental losses for many low cost photovoltaic technologies. We report a low cost, solution processable solar cell, based on a highly crystalline perovskite absorber with intense visible to near infrared absorptivity, that has a power conversion efficiency of 10.9% in a single junction device under simulated full sunlight. This "meso superstructured solar cell" exhibits exceptionally few fundamental energy losses; it can generate open circuit photovoltages of more than 1.1 volts, despite the relatively narrow absorber band gap of 1.55 electron volts. The functionality arises from the use of mesoporous alumina as an inert scaffold that structures the absorber and forces electrons to reside in and be transported through the perovskite.
author_names: Michael M Lee

Joel Teuscher

Tsutomu Miyasaka

Takurou N Murakami

Henry J Snaith
title: Efficient Hybrid Solar Cells Based on Meso Superstructured Organometal Halide Perovskites
venue: Science
year: 2012

abstract: Recently, inorganic and hybrid light absorbers such as quantum dots and organometal halide perovskites have been studied and applied in fabricating thin film photovoltaic devices because of their low cost and potential for high efficiency. Further boosting the performance of solution processed thin film solar cells without detrimentally increasing the complexity of the device architecture is critically important for commercialization. Here, we demonstrate photocurrent and efficiency enhancement in meso superstructured organometal halide perovskite solar cells incorporating core shell Au@SiO2 nanoparticles (NPs) delivering a device efficiency of up to 11.4% We attribute the origin of enhanced photocurrent to a previously unobserved and unexpected mechanism of reduced exciton binding energy with the incorporation of the metal nanoparticles, rather than enhanced light absorption. Our findings represent a new aspect and lever for the application of metal nanoparticles in photovoltaics and could lead to facile tuning of exciton binding energies in perovskite semiconductors.
author_names: Wei Zhang

Michael Saliba

Samuel D Stranks

Yao Sun

Xian Shi

Ulrich B Wiesner

Henry J Snaith
title: Enhancement of perovskite based solar cells employing core shell metal nanoparticles.
venue: Nano letters
year: 2013

abstract: To date, numerous approaches have been developed for fabricating high quality organometal halide perovskite thin films, however, perovskite films obtained by such methods reveal a brown or dark brown color, which might restrain their light absorption ability. Here we report a route to synthesize dark blue mirror like perovskite dense films via a two step spin coating process assisted by treatment of nonpolar solvent scouring. Photovoltaic cells based on such dark blue films demonstrate a high short circuit current density (Jsc) of ~23 mA cm 2 and a power conversion efficiency (PCE) of 16.1% Our method would provide a new candidate method for the fabrication of perovskite solar cells with high performance.
author_names: Jianhang Qiu

Wang Gaoxiang

Wenjing Xu

Jin Qun

Lusheng Liu

Bing-Ping Yang

Tai Kaiping

Anyuan Cao

Xin Jiang
title: Dark blue mirror like perovskite dense films for efficient organic inorganic hybrid solar cells
year: 2016

abstract: For efficient hybrid solar cells based on organometal halide perovskites, the real origin of the I V hysteresis became a big issue and has been discussed widely. In this study, simulated I V curves.
author_names: Ludmila Cojocaru

Satoshi Uchida

P V V Jayaweera

Shoji Kaneko

Jotaro Nakazaki

Takaya Kubo

Hiroshi Segawa
title: Origin of the Hysteresis in I V Curves for Planar Structure Perovskite Solar Cells Rationalized with a Surface Boundary induced Capacitance Model
year: 2015

abstract: Organometal halide perovskites are promising solar cell materials for next generation photovoltaic applications. The long carrier lifetime and diffusion length of these materials make them very attractive for use in light absorbers and carrier transporters. While these aspects of organometal halide perovskites have attracted the most attention, the consequences of the Rashba effect, driven by strong spin orbit coupling, on the photovoltaic properties of these materials are largely unexplored. In this work, taking the electronic structure of methylammonium lead iodide as an example, we propose an intrinsic mechanism for enhanced carrier lifetime in 3D Rashba materials. Based on first principles calculations and a Rashba spin orbit model, we demonstrate that the recombination rate is reduced due to the spin forbidden transition. These results are important for understanding the fundamental physics of organometal halide perovskites and for optimizing and designing the materials with better performance. The proposed mechanism including spin degrees of freedom offers a new paradigm of using 3D Rashba materials for photovoltaic applications. The organometal halide perovskites (OMHPs) have attracted significant attention due to the rapid increase in their photovoltaic power conversion efficiency. In the past 2 years, the reported efficiency of OMHP based solar cells has almost doubled from 9.7%1 to over 20%,2 4 making OHMPs very promising for low cost and high efficiency photovoltaics. Methylammonium lead iodide, CH3NH3PbI3 (MAPbI3) and other closely related hybrid perovskites such as Cl doped and Br doped MAPbI3 (MAPbI3 xClx and MAPbI3 xBrx) (NH2)2CHPbI3 (formamidinium lead iodide, FAPbI3) and Sn doped MAPbI3 (MAPbxSn1 xI3) all display band gaps (1.1 to 2.1 eV) in the visible light region, favorable for photovoltaic applications.5 13 The class of materials also possesses strong light absorption, fast charge generation and high carrier mobility.14,15 In particular, exceptionally long carrier lifetime and diffusion length have been observed in MAPbI3 and MAPbI3 xClx, making them better solar cell candidates than other semiconductors with similar band gaps and absorption coefficients.16 18 Intense research has been directed toward understanding and further enhancing the long carrier lifetime and diffusion length in OMHPs. Previous studies reported a relatively low defect 2 concentration in MAPbI3, which reduces the scattering centers for nonradiative charge carrier recombination. Recently, it has been suggested that the spatial carrier segregation caused by disorder induced localization24 or domains acting as internal p n junctions25 27 may reduce the recombination rate. Though many of the OMHPs are 3D Rashba materials driven by strong spin orbit coupling (SOC) and bulk ferroelectricity,28 31 the effects of spin and orbital degrees of freedom on photovoltaic applications are largely unexplored beyond band gap engineering.29 In this work, we focus on an intrinsic mechanism for the enhancement of long carrier lifetime due to the Rashba splitting. Using first principles calculations and effective models, we find that the Rashba splitting arising from SOC under inversion symmetry breaking can result in spin allowed and spin forbidden recombination channels. The spin forbidden recombination path has a significantly slower transition rate due to the mismatch of spin and momentum. The spin allowed recombination path, though kinetically favorable, can be suppressed under appropriate spin texture due to the low population of free carriers. Taking the electronic structures of MAPbI3 under various distortions as examples, we show that the proposed mechanism is possible under room temperature, and is potentially responsible for the long carrier lifetime in OMHPs. This spindependent recombination mechanism highlights the possibility of using 3D Rashba materials for efficient photovoltaic applications. Fig. 1 illustrates the mechanism for enhancing the carrier lifetime in a generic 3D Rashba material. The strong spin orbit coupling effect from heavy elements (e.g. Pb, Sn, I and Br) and the polar distortion (e.g. aligned molecular dipoles in OMHPs) give rise to the Rashba effect, which lifts the two fold degeneracy of bands near the band gap. Near the band gap, the spin degeneracies of the conduction and valence bands are lifted, giving rise to "inner" and "outer" bands with opposite spin textures, characterizing spin rotation direction as "clockwise" (kh 1) and "counterclockwise" (kh +1) (Fig. 1) The photo excitation process creates free electrons and holes, which can quickly relax to band extrema in the presence of inelastic phonon scattering. When the spin textures of conduction band minimum (CBM) and valence band maximum (VBM) are opposite, the radiative recombination of Ckh= 1 Vkh=+1 is a spin forbidden transition due
author_names: Fan Zheng

Liang Z Tan

Shi Liu

Andrew M Rappe
title: Rashba Spin Orbit Coupling Enhanced Carrier Lifetime in Organometal Halide Perovskites
year: 2015

abstract: Hybrid solar cells based on organometal halide perovskite absorbers have recently emerged as promising class for cost and energy efficient photovoltaics. So far, unraveling the morphology of the different materials within the nanostructured absorber layer has not been accomplished. Here, we present the first visualization of the mesoporous absorber layer in a perovskite solar cell from analytical transmission electron microscopy studies. Material contrast is achieved by electron spectroscopic imaging. We found that infiltration of the hole transport material into the scaffold is low and inhomogeneous. Furthermore, our data suggest that the device performance is strongly affected by the morphology of the TiO2 scaffold with a fine grained structure being disadvantageous.
author_names: Diana Nanova

Anne Katrin Kast

Martin Pfannmoller

Christian Muller

Lisa Veith

Irene Wacker

Michaela Agari

Wilfried Hermes

Peter Erk

Wolfgang Kowalsky

Rasmus R Schroder

Robert Lovrincic
title: Unraveling the nanoscale morphologies of mesoporous perovskite solar cells and their correlation to device performance.
venue: Nano letters
year: 2014

abstract: Hybrid perovskites have recently seen an unprecedented improvement in the power conversion efficiency in photovoltaics devices, and therefore are very promising materials for developing efficient and low cost single junction solar cells [1 3] However, a critical issue is the limited understanding of the correlation between the degree of crystallinity and the emergent perovskite/hole (or electron) transport layer on device performance as well as photo stability. Los Alamos National laboratory (LANL) developed an efficient growth procedure for 3D halide perovskites in inverted perovskite cell architecture using PEDOT PSS as a p type hole transporting material (HTM) [4] The initial collaboration between FOTON/ISCR and LANL led to the observation of a reversible self healing mechanism under light soaking [5] and showed that the aging of the precursor solution plays a role in the nucleation of the perovskite crystallites [6] In this study, we show that growth of methylammonium lead perovskites (MAPbI3) on nickel oxide (NiO) HTM, results in the formation of ordered and crystalline thin films with enhanced crystallinity, leading to characteristic XRD Bragg peak width reminiscent of exclusively observed in the tetragonal phase in single crystals. Photo physical and interface sensitive measurements reveal a reduced trap density at the MAPbI3 perovskite/NiO interface in comparison with perovskites grown on PEDOT: PSS. Photovoltaic cells exhibit a high open circuit voltage (1.12 V) indicating a nearideal energy band alignment. Moreover, we observe photo stability of photovoltaic devices up to 10 Suns, which is a direct result of the enhanced crystallinity of perovskite thin films on NiO. These results elucidate the critical role of the quality of the perovskite/HTL interface in rendering highperformance and photo stable optoelectronic devices [7] [1] Lee, M. M. Teuscher, J. Miyasaka, T. Murakami, T. N. Snaith, H. J. "Efficient Hybrid Solar Cells Based on Meso Superstructured Organometal Halide Perovskites" Science 338, 643 (2012) [2] Burschka, J. et al. "Sequential deposition as a route to high performance perovskitesensitized solar cells" Nature 499, 316 319 (2013) [3] Jeon, N. J. et al. "Solvent engineering for high performance inorganic organic hybrid perovskite solar cells" Nat. Mater. 13, 897 903 (2014) [4] Nie, W. et al, "High efficiency solution processed perovskite solar cells with millimeterscale grains" Science 347, 522 (2015) [5] Nie, W. et al, "Light activated photocurrent degradation and self healing in perovskite solar cells" Nat. Comm. 7, 11574 (2016) [6] Tsai, H. et al," Effect of Precursor Solution Aging on the Crystallinity and Photovoltaic Performance of Perovskite Solar Cells" Adv. Ener. Mat. 7, 1602159 (2017) [7] Nie, W. et al, Adv. Mater. (In press)
author_names: Olivier Durand

Wanyi Nie

Hsinhan Tsai

Reza Asadpour

Jean-Christophe Blancon

Fangze Liu

Constantinos C Stoumpos

Joseph W Strzalka

Jared J Crochet

Pulickel M Ajayan

Boubacar Traore

Mikael Kepenekian

Claudine Katan

Sergei Tretiak

Mercouri G Kanatzidis

Muhammad A Alam

Jacky Even

Aditya D Mohite
title: Critical role of Interface and perovskite lattice in high efficiency and photostable solar cells
year: 2017

abstract: Due to their outstanding optical properties and superior charge carrier mobilities, organometal halide perovskites have been widely investigated in photodetection and solar cell areas. In perovskites photodetection devices, their high optical absorption and excellent quantum efficiency contribute to the responsivity, even the specific detectivity. In this work, we developed a lateral phototransistor based on mesoscopic graphene/perovskite heterojunctions. Graphene nanowall shows a porous structure, and the spaces between graphene nanowall are much appropriated for perovskite crystalline to mount in. Hot carriers are excited in perovskite, which is followed by the holes' transfer to the graphene layer through the interfacial efficiently. Therefore, graphene plays the role of holes' collecting material and carriers' transporting channel. This charge transfer process is also verified by the luminescence spectra. We used the hybrid film to build phototransistor, which performed a high responsivity and specific detectivity of 2.0 x 103 A/W and 7.2 x 1010 Jones, respectively. To understand the photoconductive mechanism, the perovskite's passivation and the graphene photogating effect are proposed to contribute to the device's performance. This study provides new routes for the application of perovskite film in photodetection.
author_names: Dahua Zhou

Leyong Yu

Peng-Li Zhu

Hongquan Zhao

Shuanglong Feng

Jun Shen
title: Lateral Structured Phototransistor Based on Mesoscopic Graphene/Perovskite Heterojunctions
venue: Nanomaterials
year: 2021

abstract: A sensitized solar cell introduced by O'Regan and Gratzel in 1991 was one of the milestones in third generation hybrid solar cells because of the novelty of its architecture, ease of its fabrication, cost effectiveness and good efficiency. Despite persistent efforts made by various groups around the world for over 20 years, the efficiency of DSSCs had not crossed 13% Very recently however, a major path breaking advance has been realized in the domain of solid state sensitized solar cells with the introduction of organometal halide perovskites as efficient alternatives to liquid electrolyte based DSSCs. These new systems have already shown efficiency values of about 15 16% and hold great promise for even higher efficiency (20% at lower cost. Interestingly, the optoelectronic properties of organometal halide perovskites can be tuned by varying the organic cation sizes, metal ions, or the halide anions. Several research groups have shown that complete replacement of I with other halide ions such as Br or Cl leads to increase in the energy gap and therefore lower photocurrents and efficiency. However the presence of mixed halides in the perovskite structure such as CH3NH3PbI2Cl can lead to higher photovoltaic performance because of the increase in the carrier diffusion length (B1 mm) without an appreciable increase in the band gap. Chung et al. showed that doping inorganic perovskite CsSnI3 with 5% fluorine could dramatically improve the photocurrent density by nearly 40% However, to the best of our knowledge, there are no reports of mixed halide organometal perovskite systems with I and F ions applied in solar cells. Importantly, Mosconi et al. have shown that the mixed halide perovskite system consists of two different structures whose stability decreases from I to F along the column VIIA in the periodic table. Therefore it is difficult to stabilize I and F based mixed halide perovskite systems. Herein, we report an interesting strategy to incorporate fluoride ions in the perovskite structure via partial substitution of I by BF4 Importantly, I and BF4 both have nearly the same ionic radius, which makes the incorporation of BF4 feasible in the structure. We further show that I and BF4 based mixed halide perovskite possesses an order of magnitude higher low frequency conductivity than I based perovskite without an appreciable change in the absorption onset. In order to incorporate BF4 within the perovskite structure, the organic salt CH3NH3BF4 was prepared using methylamine and tetrafluoroboric acid solutions. The hybrid perovskite films were prepared using chemical vapor deposition of organic salt CH3NH3BF4 on preheated PbI2 films whereas the powder of hybrid perovskite was prepared using the solid state route with a mixture of organic salt and PbI2. The detailed experimental procedure is given in the ESI. The phase of the synthesized perovskite was confirmed using X ray diffraction measurements. Fig. 1(a) shows the XRD pattern of synthesized CH3NH3PbI(3 x)(BF4)x perovskite film on glass. The crystal structure of CH3NH3PbI(3 x)(BF4)x perovskite is found to be identical to the conventional CH3NH3PbI3 tetragonal perovskite structure as indicated by the appearance of peaks at 14.01, 28.31, 31.81 and 43.21 for the (110) (220) (310) and (330) planes, respectively. The presence of sharp peaks in the X ray diffraction pattern indicates the highly crystalline nature of the perovskite film. In order to confirm the presence of BF4 groups in the perovskite structure, we carried out the ATR FTIR study of the CH3NH3PbI(3 x)(BF4)x films on glass. Fig. 1(b) shows the characteristic stretching vibration peaks of BF4 at 1135 cm 967 cm 524 cm 1084 cm 952 cm 1 (for symmetric stretching) and 1053 cm 1 (B F stretching) which are otherwise absent in the CH3NH3PbI3 perovskite. a Centre of Excellence in Solar Energy, National Chemical Laboratory (CSIR NCL) Dr. Homi Bhabha Road, Pune, India b Academy of Scientific and Innovative Research (AcSIR) Network Institute of Solar Energy (CSIR NISE) New Delhi, India. E mail: satyawan.nagane@gmail.com, sb.ogale@ncl.res.in Electronic supplementary information (ESI) available: Experimental details and Fig. S1 S4. See DOI: 10.1039/c4cc04537h Received 15th June 2014, Accepted 4th July 2014
author_names: Satyawan Nagane

Umesh Pandharinath Bansode

Onkar S Game

Shraddha Y Chhatre
title: CH 3 NH 3 PbI 3 x BF 4 x molecular ion substituted hybrid perovskite
year: 2014

abstract: While the field of perovskite based optoelectronics has mostly been dominated by photovoltaics, light emitting diodes and transistors, semiconducting properties peculiar to perovskites make them interesting candidates for innovative and disruptive applications in light signal detection. Perovskites combine effective light absorption in the broadband range with good photo generation yield and high charge carrier mobility, which combination provides promising potential for exploiting sensitive and fast photodetectors that are targeted for image sensing, optical communication, environmental monitoring, or chemical/biological detection. Currently, organic inorganic hybrid and all inorganic halide perovskites with controlled morphologies of polycrystalline thin films, nano particles/wires/sheets, and bulk single crystals have shown key figure of merit features in terms of their responsivity, detectivity, noise equivalent power, linear dynamic range, and response speed. The sensing region has been covered from ultraviolet visible near infrared (UV Vis NIR) to gamma photons, based on two or three terminal device architectures. Diverse photoactive materials and devices with superior optoelectronic performances have stimulated attention from researchers in multidisciplinary areas. We offer a comprehensive overview of the recent progress of perovskite based photodetectors, focusing on versatile compositions, structures, and morphologies of constituent materials, and diverse device architectures toward the superior performance metrics. Combining the advantages of both organic semiconductors (facile solution processability) and inorganic semiconductors (high charge carrier mobility) perovskites are expected to replace commercial silicon for future photodetection applications. The optical and electronic properties of noble metallic nanoparticles can be exploited to enhance the performance of inorganic/organic photodetectors. We integrated a uniformly distributed layer of Au nanorods (AuNRs) into vertically structured perovskite photoconductive photodetectors and report, as a result, perovskite AuNR hybrid photodetectors that exhibit significant photocurrent enhancements. Ultimately it achieves a responsivity of ~320 A/W at a low driving voltage of 1 V. This is an improvement of 60% compared to the responsivity of pristine devices ~200 A/W) The high responsivity and low driving voltage place this device among the highest performing perovskite based thin film photoconductive photodetectors reported. We characterized the stability and linearity of the photoresponse following repeated light/dark cycles. The hybrid device also shows a fast response (with the decay time of ~95 ns) compared to pristine devices ~230 ns) The improvements in photodetection performance are attributed to plasmon enhanced optical absorption, as well as advances in charge extraction and transport. Metal halide perovskites have rapidly advanced thin film photovoltaic performance; as a result, the materials' ob served instabilities urgently require a solution. Using density functional theory (DFT) we show that a low energy of formation, exacerbated in the presence of humidity, explains the propensity of perovskites to decompose back into their precursors. We find, also using DFT, that intercalation of phenylethylammonium between perovskite layers in troduces quantitatively appreciable van der Waals interactions; and these drive an increased formation energy and should therefore improve material stability. Here we report the reduced dimensionality (quasi 2D) perovskite films that exhibit improved stability while retaining the high performance of conventional three dimensional perovskites. Continuous tuning of the dimensionality, as assessed using photophysical studies, is achieved by the choice of stoi chiometry in materials synthesis. We achieve the first certified hysteresis free solar power conversion in a planar per ovskite solar cell, obtaining a 15.3% certified PCE, and observe greatly improved performance longevity. The same protocol was applied to develop highly stable and efficient photodectors in diverse device configurations. Organometal halide perovskites exhibit large bulk crystal domain sizes, rare traps, excellent mobilities, and carriers that are free at room temperature properties that support their excellent performance in charge separating devices. In devices that rely on the forward injection of electrons and holes, such as light emitting diodes (LEDs) excellent mobilities contribute to the efficient capture of nonequilibrium charge carriers to rare nonradiative centres. Moreover, the lack of bound excitons weakens the competition of desired radiative over undesired nonradiative recombination. Here we also report a perovskite mixed material, one comprised of a series of differently quantum size tuned grains, that funnels photoexcitations to the lowest bandgap light emitter in the mixture. The materials function as charge carrier concentrators, ensuring that radiative recombination successfully outcompetes trapping and hence nonradiative recombination. We use the new material to build devices that exhibit an external quantum efficiency (EQE) of 8.8% and a radiance of 80 Wsr 1m 2. These represent the brightest and most efficient solution processed near infrared LEDs to date. Here we show that, by concentrating photoexcited states into a small subpopulation of radiative domains, one can achieve a high quantum yield even at low excitation intensities. We tailor the composition of quasi 2D perovskites to direct the energy transfer into the lowest bandgap minority phase, and to do so faster than it is lost to non radiative centres. The new material exhibits 60% photoluminescence quantum yield at excitation intensities as low as 1.8 mW/cm2, yielding a ratio of quantum yield to excitation intensity of 0.3 cm2/mW; this represents a two orders of magnitude decrease in the excitation power required to reach high efficiency compared to the best prior reports. Using this strategy, we report LEDs with EQEs of 7.4% and a high luminescence of 8400 cd/m2.
author_names: Dong Ha Kim

Huan Mei Wang

Ju Won Lim

Li Na Quan

Ilgeum Lee

Edward H Sargent
title: Optoelectronic hybrid perovskite materials and devices (Conference Presentation)
year: 2018