Enhancing the Optoelectronic Performance of Perovskite Solar Cells via a Textured CH3NH3PbI3 Morphology

Perovskite‐based solar cells are generally assembled as planar structures comprising a flat organoammonium metal halide perovskite layer, or mesoscopic structures employing a mesoporous metal‐oxide scaffold into which the perovskite material is infiltrated. To present, little attention has been directed toward the texturing of the perovskite material itself. Herein, a textured CH₃NH₃PbI₃ morphology formed through a thin mesoporous TiO₂ seeding layer and a gas‐assisted crystallization method is reported. The textured morphology comprises a multitiered nanostructure, which allows for significant improvements in the light harvesting and charge extraction performance of the solar cells. Due to these improvements, average short‐circuit current densities for a batch of 28 devices are in excess of 22 mA cm^?2, and the maximum recorded power conversion efficiency is 16.3%. The performance gains concomitant with this textured CH₃NH₃PbI₃ morphology provide further insights into how control of the perovskite microstructure can be used to enhance the cell performance.     

Thin Films of Dendritic Anatase Titania Nanowires Enable Effective Hole‐Blocking and Efficient Light‐Harvesting for High‐Performance Mesoscopic Perovskite Solar Cells

To achieve high‐performance perovskite solar cells, especially with mesoscopic cell structure, the design of the electron transport layer (ETL) is of paramount importance. Highly branched anatase TiO₂ nanowires (ATNWs) with varied orientation are grown via a facile one‐step hydrothermal process on a transparent conducting oxide substrate. These films show good coverage with optimization obtained by controlling the hydrothermal reaction time. A homogeneous methyl­ammonium lead iodide (CH₃NH₃PbI₃) perovskite thin film is deposited onto these ATNW films forming a bilayer architecture comprising of a CH₃NH₃PbI₃ sensitized ATNW bottom layer and a CH₃NH₃PbI₃ capping layer. The formation, grain size, and uniformity of the perovskite crystals strongly depend on the degree of surface coverage and the thickness of the ATNW film. Solar cells constructed using the optimized ATNW thin films (220 nm in thickness) yield power conversion efficiencies up to 14.2% with a short‐circuit photocurrent density of 20.32 mA cm^?2, an open‐circuit photovoltage of 993 mV, and a fill factor of 0.70. The dendritic ETL and additional perovskite capping layer efficiently capture light and thus exhibit a superior light harvesting efficiency. The ATNW film is an effective hole‐blocking layer and efficient electron transport medium for excellent charge separation and collection within the cells.     

In situ recycle of PbI2 as a step towards sustainable perovskite solar cells

The development of organometal halide perovskite solar cells has grown rapidly and the highest efficiency of the devices has recently surpassed 22%. Because these solar cells contain toxic lead, a sustainable strategy is required to prevent environmental pollution and avoid healthy hazard caused by possible lead outflow. Here, in situ recycling PbI₂ from thermal decomposition CH₃NH₃PbI₃ perovskite films for efficient perovskite solar cells was developed. The thermal behavior of CH₃NH₃PbI₃ perovskite and its individual components were examined by thermogravimetric analysis. By optimizing the process of thermal decomposition CH₃NH₃PbI₃ film, the complete conversion from CH₃NH₃PbI₃ to pure PbI₂ layer with a mesoporous scaffold was achieved. The mesoporous structure readily promotes the conversion efficiency of perovskite and consequently results in high‐performance device. A perovskite crystal growth mechanism on the mesoporous PbI₂ structure was proposed. These results suggest that in situ recycled PbI₂ scaffolds can be a new route in manipulating the morphology of the perovskite active layer, providing new possibilities for high performance. Meanwhile, the risk of lead outflow can be released, and the saving‐energy fabrication of efficient solar cells can be realized.     

A Facile Preparative Route of Nanoscale Perovskites over Mesoporous Metal Oxide Films and Their Applications to Photosensitizers and Light Emitters

By two‐step sequential Pb²⁺ adsorption and reaction with methylammonium‐iodide (MAI) or ‐bromide (MABr) at a low concentration level of 0.06–0.10 m over mesoporous TiO₂ or ZrO₂ film, a well‐defined nanoscale CH₃NH₃PbI₃ (MAPbI₃) photosensitizer or CH₃NH₃PbBr₃ (MAPbBr₃) light emitter could be prepared in situ, respectively in a reproducible and atom‐economical way. The as‐prepared nanoscale perovskites are compared with their thin film counterparts in terms of light absorption/emission, crystallinity, surface morphology, and energy‐conversion efficiency. The nanoscale perovskite‐decorated films display more transparency than the bulky film due to the much lower amount deposited, while blueshifted and overwhelmingly brighter photoluminescence is observed in the “nano” relative to the “bulk” due to quantum size confinement. Transmission electron microscopy images also clearly show that a few nanometer‐sized perovskite dots are deposited homogeneously over the surface of TiO₂‐ or ZrO₂‐particulate film in the course of the current preparative route. When the nano‐MAPbI₃ is tested as a photosensitizer in a solid‐state dye‐sensitized solar cell configuration with a very thin ( ≈ 650 nm) TiO₂ mesoporous film, it has a promising initial power conversion efficiency of 6.23%, which outperformed the result of 2.28% from a typical organic molecular dye coded as MK‐2.     

Function Follows Form: Correlation between the Growth and Local Emission of Perovskite Structures and the Performance of Solar Cells

Understanding the relationship between the growth and local emission of hybrid perovskite structures and the performance of the devices based on them demands attention. This study investigates the local structural and emission features of CH₃NH₃PbI₃, CH₃NH₃PbBr₃, and CH(NH₂)₂PbBr₃ perovskite films deposited under different yet optimized conditions using X‐ray scattering and cathodoluminescence spectroscopy, respectively. X‐ray scattering shows that a CH₃NH₃PbI₃ film involving spin coating of CH₃NH₃I instead of dipping is composed of perovskite structures exhibiting a preferred orientation with [202] direction perpendicular to the surface plane. The device based on the CH₃NH₃PbI₃ film composed of oriented crystals yields a relatively higher photovoltage. In the case of CH₃NH₃PbBr₃, while the crystallinity decreases when the HBr solution is used in a single‐step method, the photovoltage enhancement from 1.1 to 1.46 V seems largely stemming from the morphological improvements, i.e., a better connection between the crystallites due to a higher nucleation density. Furthermore, a high photovoltage of 1.47 V obtained from CH(NH₂)₂PbBr₃ devices could be attributed to the formation of perovskite films displaying uniform cathodoluminescence emission. The comparative analysis of the local structural, morphological, and emission characteristics of the different perovskite films supports the higher photovoltage yielded by the relatively better performing devices.     

Efficient Perovskite Hybrid Photovoltaics via Alcohol‐Vapor Annealing Treatment

In this work, alcohol‐vapor solvent annealing treatment on CH₃NH₃PbI₃ thin films is reported, aiming to improve the crystal growth and increase the grain size of the CH₃NH₃PbI₃ crystal, thus boosting the performance of perovskite photovoltaics. By selectively controlling the CH₃NH₃I precursor, larger‐grain size, higher crystallinity, and pinhole‐free CH₃NH₃PbI₃ thin films are realized, which result in enhanced charge carrier diffusion length, decreased charge carrier recombination, and suppressed dark currents. As a result, over 43% enhanced efficiency along with high reproducibility and eliminated photocurrent hysteresis behavior are observed from perovskite hybrid solar cells (pero‐HSCs) where the CH₃NH₃PbI₃ thin films are treated by methanol vapor as compared with that of pristine pero‐HSCs where the CH₃NH₃PbI₃ thin films are without any alcohol vapor treatment. In addition, the dramatically restrained dark currents and raised photocurrents give rise to over ten times enhanced detectivities for perovskite hybrid photodetectors, reaching over 10¹³ cm Hz^1/2 W^?1 (Jones) from 375 to 800 nm. These results demonstrate that the method provides a simple and facile way to boost the device performance of perovskite photovoltaics.     

Enhanced Device Performance of Perovskite Photovoltaics by Magnetic Field‐Aligned Perovskites‐Magnetic Nanoparticles Composite Thin Film

Perovskite photovoltaics have drawn great attention in both academic and industrial sectors in the past decade. To date, impressive device performance has been achieved in state‐of‐the‐art device architectures through morphological manipulation and generic interface engineering. In this study, enhanced device performance of perovskite photovoltaics by magnetic field‐aligned CH₃NH₃PbI₃‐mixed Fe₃O₄ magnetic nanoparticles (CH₃NH₃PbI₃:Fe₃O₄) composite thin films is reported. It is found that magnetic field‐aligned CH₃NH₃PbI₃:Fe₃O₄ composite thin films possess superior film morphology, boosted and balanced charge carrier mobility, and suppressed trap density. Moreover, perovskite photovoltaics by magnetic field‐aligned CH₃NH₃PbI₃:Fe₃O₄ composite thin films exhibit suppressed charge carrier recombination and shorter charge carrier extraction time. As a result, perovskite solar cells by magnetic field‐aligned CH₃NH₃PbI₃:Fe₃O₄ composite thin films exhibit 20.23% power conversion efficiency with significantly reduced photocurrent hysteresis. Moreover, perovskite photodetectors by magnetic field‐aligned CH₃NH₃PbI₃:Fe₃O₄ composite thin films exhibit a photoresponsivity of 858 mA W^?1, a photodetectivity over 10¹³ Jones (1 Jones = 1 cm Hz^1/2 W^?1) and a linear dynamic range over 160 dB at room temperature. All these device performance parameters are significantly better than those by pristine CH₃NH₃PbI₃ thin film. Thus, these studies provide a facile way to boost device performance of perovskite photovoltaics.     

Monitoring the Formation of a CH3NH3PbI3–xClx Perovskite during Thermal Annealing Using X‐Ray Scattering

Grazing incidence wide and small angle X‐ray scattering (GIWAXS and GISAXS) measurements have been used to study the crystallization kinetics of the organolead halide perovskite CH₃NH₃PbI_3–xCl_x during thermal annealing. In situ GIWAXS measurements recorded during annealing are used to characterize and quantify the transition from a crystalline precursor to the perovskite structure. In situ GISAXS measurements indicate an evolution of crystallite sizes during annealing, with the number of crystallites having sizes between 30 and 400 nm increasing through the annealing process. Using ex situ scanning electron microscopy, this evolution in length scales is confirmed and a concurrent increase in film surface coverage is observed, a parameter crucial for efficient solar cell performance. A series of photovoltaic devices are then fabricated in which perovskite films have been annealed for different times, and variations in device performance are explained on the basis of X‐ray scattering measurements.     

High‐Quality Cuboid CH3NH3PbI3 Single Crystals for High Performance X‐Ray and Photon Detectors

Organic–inorganic halide hybrid perovskite materials are promising materials for X‐ray and photon detection due to their superior optoelectronic properties. Single‐crystal (SGC) perovskites have increasingly attracted attention due to their substantially low crystal defects, which contribute to improving the figures of merit of the devices. Cuboid CH₃NH₃PbI₃ SGC with the naturally favorable geometry for device fabrication is rarely reported in X‐ray and photon detection application. The concept of seed dissolution‐regrowth to improve crystal quality of cuboid CH₃NH₃PbI₃ SGC is proposed and a fundamental understanding of the nucleation and growth is provided thermodynamically. The X‐ray detector fabricated from cuboid CH₃NH₃PbI₃ SGC demonstrates the firstly reported high sensitivity of 968.9 µC^?1 Gy^?1 cm^?2 under ?1 V bias. The results also show that the favorable crystal orientation and high quality of cuboid CH₃NH₃PbI₃ leads to better responsivity and faster response speed than the more common dodecahedral CH₃NH₃PbI₃ in photodetection. Consequently, the work paves a way to synthesize high‐quality perovskite SGCs and benefits the application of MAPbI₃ SGCs with preferred crystal orientation and favorable crystal geometry for emerging device applications.     

Zwitterion Coordination Induced Highly Orientational Order of CH3NH3PbI3 Perovskite Film Delivers a High Open Circuit Voltage Exceeding 1.2 V

The organic–inorganic halide CH₃NH₃PbI₃ (MAPbI₃) has been the most commonly used light absorber layer of perovskite solar cells (PSCs); however, solution‐processed MAPbI₃ films usually suffer from random crystal orientation and high trap density, resulting in inferior power conversion efficiency (PCE) with open circuit voltage (V_oc) being typically below 1.2 V for PSC devices. Herein, for the first time an imidazole sulfonate zwitterion, 4‐(1H‐imidazol‐3‐ium‐3‐yl)butane‐1‐sulfonate (IMS), is applied as a bifunctional additive in regular‐structure planar heterojunction PSC devices to regulate the crystal orientation, yielding highly ordered MAPbI₃ film and passivating the trap states of the film. Such a dual effect of IMS is fulfilled via coordination interactions between the sulfonate moiety of IMS with the Pb2⁺ ion and the electrostatic interaction between the imidazole of IMS with the I^– ion of MAPbI₃. As a result, under a optimized IMS doping ratio of 0.5 wt%, the PSC device exhibits a significant increase in PCE from 18.77% to 20.84%, with suppressed current–voltage hysteresis and promoted ambient stability. Moreover, a high V_oc of 1.208 V is achieved under a higher IMS doping ratio of 1.2 wt%, which is the highest V_oc for regular‐structure MAPbI₃ planar PSC devices based on TiO₂ electron transport layer.     

The Role of Chlorine in the Formation Process of “CH3NH3PbI3‐xClx” Perovskite

CH₃NH₃PbI_3‐xCl_x is a commonly used chemical formula to represent the methylammonium lead halide perovskite fabricated from mixed chlorine‐ and iodine‐containing salt precursors. Despite the rapid progress in improving its photovoltaic efficiency, fundamental questions remain regarding the atomic ratio of Cl in the perovskite as well as the reaction mechanism that leads to its formation and crystallization. In this work we investigated these questions through a combination of chemical, morphological, structural and thermal characterizations. The elemental analyses reveal unambiguously the negligible amount of Cl atoms in the CH₃NH₃PbI_3‐xCl_x perovskite. By studying the thermal characteristics of methylammonium halides as well as the annealing process in a polymer/perovskite/FTO glass structure, we show that the formation of the CH₃NH₃PbI_3‐xCl_x perovskite is likely driven by release of gaseous CH₃NH₃Cl (or other organic chlorides) through an intermediate organometal mixed halide phase. Furthermore, the comparative study on CH₃NH₃I/PbCl₂ and CH₃NH₃I/PbI₂ precursor combinations with different molar ratios suggest that the initial introduction of a CH₃NH₃⁺ rich environment is critical to slow down the perovskite formation process and thus improve the growth of the crystal domains during annealing; accordingly, the function of Cl^? is to facilitate the release of excess CH₃NH₃⁺ at a relatively low annealing temperatures.     

Improved performance of perovskite solar cells with a TiO2/MoO3 core/shell nanoparticles doped PEDOT:PSS hole-transporter

We demonstrate improved performance of inverted planar heterojunction CH₃NH₃PbI_3-xCl_x perovskite solar cells with a TiO₂/MoO₃ core/shell nanoparticles (NPs) doped poly(3,4-ethylene dioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) hole-transporting layer (HTL). TiO₂/MoO₃ Core/shell NPs with size of approximately 40 nm are successfully prepared with a simple wet solution method and are interspersed into PEDOT: PSS layer to construct the HTL. The optimized device shows a high power conversion efficiency of 13.63%, which is dramatically improved compared with the reference device with a pristine PEDOT:PSS HTL. The improvement is mainly attributed to the increased crystalline of the CH₃NH₃PbI_3-xCl_x film with large-scale domains and a compact morphology. More interesting, the cells exhibit superior stability in ambient conditions, which is attributed to the inhibited penetration of moisture due to the compact morphology of the CH₃NH₃PbI_3-xCl_x film and the reduced hygroscopicity of the PEDOT:PSS film.     

Synergistic Effect of PbI2 Passivation and Chlorine Inclusion Yielding High Open‐Circuit Voltage Exceeding 1.15 V in Both Mesoscopic and Inverted Planar CH3NH3PbI3(Cl)‐Based Perovskite Solar Cells

Enhancing open‐circuit voltage in CH₃NH₃PbI₃(Cl) perovskite solar cells has become a major challenge for approaching the theoretical limit of the power conversion efficiency. Here, for the first time, it is demonstrated that the synergistic effect of PbI₂ passivation and chlorine incorporation via controlling the molar ratio of PbI₂, PbCl₂ (or MACl), and MAI in the precursor solutions, boosts the open‐circuit voltage of CH₃NH₃PbI₃(Cl) perovskite solar cells over 1.15 V in both mesoscopic and inverted planar perovskite solar cells. Such high open‐circuit voltage can be attributed to the enhanced photoluminescence emission and carrier lifetime associated with the reduced trap densities. The morphology and composition analysis using scanning electron microscopy, X‐ray diffraction measurements, and energy dispersive X‐ray spectroscopy confirm the high quality of the optimized CH₃NH₃PbI₃(Cl) perovskite film. On this basis, record‐high efficiencies of 16.6% for nonmetal‐electrode all‐solution‐processed perovskite solar cells and 18.4% for inverted planar perovskite solar cells are achieved.     

High‐Performance Photodetectors Based on Organometal Halide Perovskite Nanonets

The booming development of organometal halide perovskites has prompted the exploration of morphology‐engineering strategies to improve their performance in optoelectronic applications. However, the preparation of optoelectronic devices of perovskites with complex architectures and desirable properties is still highly challenging. Herein, novel CH₃NH₃PbI₃ nanonets and nanobowl arrays are fabricated facilely by using monolayer colloidal crystal (MCC) templates on different substrates. Specifically, highly ordered CH₃NH₃PbI₃ nanonets with high crystallinity are fabricated on a variety of flat substrates, whereas regular CH₃NH₃PbI₃ nanobowl arrays are produced on a coarse substrate. The photodetection performance of the CH₃NH₃PbI₃ nanonet‐based photodetectors is significantly enhanced compared to the photodetectors based on conventional CH₃NH₃PbI₃ compact films. Particularly, the nanonet photodetectors exhibit a high responsivity (10.33 A W^?1 under 700 nm monochromatic light), which is six times higher than that for the compact CH₃NH₃PbI₃ film devices, fast response speed, and good stability. Owing to the two‐dimensional arrayed structure, the CH₃NH₃PbI₃ nanonets exhibit an enhanced light harvesting ability and offer direct carrier transport pathways. Meanwhile, the MCC template brings about larger grain sizes with enhanced crystallinity. Furthermore, the perovskite nanonets can be formed on a flexible polyethylene terephthalate substrate for the fabrication of promising flexible nanonet photodetectors.     

Inhibition of Ion Migration for Reliable Operation of Organolead Halide Perovskite‐Based Metal/Semiconductor/Metal Broadband Photodetectors

Organolead halide perovskites (OHPs) have attracted extensive attention as light harvesting materials for solar cells recently, because of their high charge carrier mobility, high photoconversion efficiencies, low cost, and simple methodology. Despite these advantages, the OHPs exhibit sweep‐dependent hysteresis behavior in current–voltage characteristics films, deteriorating the reliability of devices based on the OHPs. This study demonstrates reliable high on/off ratio (I_on/I_off = 10⁴) CH₃NH₃PbI₃ broadband photodetectors with buffer layer‐free simple metal/semiconductor/metal lateral structure. At high external bias, poor on/off ratios and spikes in dark current and photocurrent are observed due to the migration of charged defect ions. The ion migration can be effectively inhibited at low external bias, and thus the devices show high I_on/I_off ratios and spike‐free dark current and photocurrent. In addition, prevention of the prepoling in the CH₃NH₃PbI₃ films by operating at the low external bias results in pronouncedly enhanced signal‐to‐noise ratios even under low intensity incident light. These results strongly propose that inhibiting the migration of charged defect ions in CH₃NH₃PbI₃ films is a key in developing reliable high performance CH₃NH₃PbI₃‐based devices.     

Improving the Extraction of Photogenerated Electrons with SnO2 Nanocolloids for Efficient Planar Perovskite Solar Cells

Great attention to cost‐effective high‐efficiency solar power conversion of trihalide perovskite solar cells (PSCs) has been hovering at high levels in the recent 5 years. Among PSC devices, admittedly, TiO₂ is the most widely used electron transport layer (ETL); however, its low mobility which is even less than that of CH₃NH₃PbI₃ makes it not an ideal material. In principle, SnO₂ with higher electron mobility can be regarded as a positive alternative. Herein, a SnO₂ nanocolloid sol with ≈3 nm in size synthesized at 60 °C was spin‐coated onto the fuorine‐doped tin oxide (FTO) glass as the ETL of planar CH₃NH₃PbI₃ perovskite solar cells. TiCl₄ treatment of SnO₂‐coated FTO is found to improve crystallization and increase the surface coverage of perovskites, which plays a pivotal role in improving the power conversion efficiency (PCE). In this report, a champion efficiency of 14.69% (J_sc = 21.19 mA cm^?2, V_oc = 1023 mV, and FF = 0.678) is obtained with a metal mask at one sun illumination (AM 1.5G, 100 mW cm^?2). Compared to the typical TiO₂, the SnO₂ ETL efficiently facilitates the separation and transportation of photogenerated electrons/holes from the perovskite absorber, which results in a significant enhancement of photocurrent and PCE.     

HPbI3: A New Precursor Compound for Highly Efficient Solution‐Processed Perovskite Solar Cells

Recently, there have been extensive research efforts on developing high performance organolead halide based perovskite solar cells. While most studies focused on optimizing the deposition processes of the perovskite films, the selection of the precursors has been rather limited to the lead halide/methylammonium (or formamidium) halide combination. In this work, we developed a new precursor, HPbI₃, to replace lead halide. The new precursor enables formation of highly uniform formamidium lead iodide (FAPbI₃) films through a one‐step spin‐coating process. Furthermore, the FAPbI₃ perovskite films exhibit a highly crystalline phase with strong (110) preferred orientation and excellent thermal stability. The planar heterojunction solar cells based on these perovskite films exhibit an average efficiency of 15.4% and champion efficiency of 17.5% under AM 1.5 G illumination. By comparing the morphology and formation process of the perovskite films fabricated from the formamidium iodide (FAI)/HPbI₃, FAI/PbI₂, and FAI/PbI₂ with HI additive precursor combinations, it is shown that the superior property of the HPbI₃ based perovskite films may originate from 1) a slow crystallization process involving exchange of H⁺ and FA⁺ ions in the PbI₆ octahedral framework and 2) elimination of water in the precursor solution state.     

Deciphering the NH4PbI3 Intermediate Phase for Simultaneous Improvement on Nucleation and Crystal Growth of Perovskite

The NH₄PbI₃‐based phase transformation is realized by simply adding NH₄I additive, in order to simultaneously control perovskite nucleation and crystal growth. Regarding the nucleation process, the NH₄⁺ with small ionic radius preferentially diffuses into the [PbI₆]^4? octahedral layer to form NH₄PbI₃, which compensates the lack of CH₃NH₃I (MAI) precipitation. The generation of NH₄PbI₃ intermediate phase results in extra heterogeneous nucleation sites and reduces the defects derived from the absence of MA⁺. Regarding the crystal growth process, the cation exchange process between MA⁺ and NH₄⁺, instead of the MAs directly entering, successfully retards the crystal growth. Such NH₄PbI₃ consumption process slows down the crystal growth, which effectively improves the perovskite quality with lowered defect density. The cooperation of these two effects eventually leads to the high‐quality perovskite with enlarged grain size, prolonged photoluminescence lifetime, lowered defect density, and increased carrier concentration, as well as the finally enhanced photovoltaic performance. Moreover, NH₃ as a byproduct further facilitates the proposed transformation process and no external residue remains even without any post‐treatment. Such methodology of introducing a novel phase transformation to simultaneously control nucleation and crystal growth processes is of universal significance for further devotion in the foreseeable perovskite solar cells (PSCs) evolution.     

High-quality CH3NH3PbI3 thin film fabricated via intramolecular exchange for efficient planar heterojunction perovskite solar cells

The high-quality CH₃NH₃PbI₃ perovskite thin film with excellent coverage and uniformity was prepared using an intramolecular exchange technology via a low-temperature, two-step sequential deposition process. The PbI₂(DMSO) complex was synthesized at room temperature without any additives and was deposited, then the CH₃NH₃I solution was deposited subsequently. The further controllable thermal annealing process resulted in the complete formation of flat and uniform CH₃NH₃PbI₃ thin film with large-size grains and (110) preferred crystallographic orientation. The perovskite solar cells (PSCs) with a very simple inverted planar heterojunction structure of ITO/PEDOT:PSS/CH₃NH₃PbI₃/PCBM/Al and without other buffer layers, e.g., C₆₀, LiF, BCP, etc., were fabricated, resulting in a power conversion efficiency (PCE) as high as 14.26%. The results suggest that the low-temperature, two-step sequential deposition process with intramolecular exchange technology provides a good route to fabricate high-quality perovskite thin film and efficient PSCs, which would match with large-scale, high-output roll-to-roll (R2R) printing/coating techniques.     

Morphological Control for High Performance,Solution‐Processed Planar Heterojunction Perovskite Solar Cells

Organometal trihalide perovskite based solar cells have exhibited the highest efficiencies to‐date when incorporated into mesostructured composites. However, thin solid films of a perovskite absorber should be capable of operating at the highest efficiency in a simple planar heterojunction configuration. Here, it is shown that film morphology is a critical issue in planar heterojunction CH₃NH₃PbI_3‐xCl_x solar cells. The morphology is carefully controlled by varying processing conditions, and it is demonstrated that the highest photocurrents are attainable only with the highest perovskite surface coverages. With optimized solution based film formation, power conversion efficiencies of up to 11.4% are achieved, the first report of efficiencies above 10% in fully thin‐film solution processed perovskite solar cells with no mesoporous layer.