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Yellow‐phase formamidinium lead iodide (δ‐FAPbI3) as a degradation product of black perovskite phase is usually unwelcome in perovskite solar cells (PSCs). However, it also shows high potential in passivating defects and protecting perovskite films from moisture intrusion due to its water‐stable nature. Herein, the utilization of δ‐FAPbI3 to construct a yellow/black heterophase bilayer is reported, in which the perovskite layer is shielded by in situ formed δ‐FAPbI3 species on the surface, for PSCs with enhanced efficiency and stability. It is found that the δ‐FAPbI3 layer with a broader bandgap than the black‐phase perovskite can efficiently suppress the charge recombination at the interface, offering a high PSC efficiency of 23.10%. More importantly, the δ‐FAPbI3‐modified devices exhibit preferable stability against various external stresses to that of the control ones. Compared to those using the disliked δ‐FAPbI3 in the literature, the strategy, which maximizes its merits in reducing the interfacial charge recombination and stabilizing the perovskite structure, is more simple yet effective to realize highly efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

The supramolecular lead iodide perovskite crystals, {[NH4(18-crown-6)]PbI3}∞ (1), (18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane), was successfully achieved by a facile solvent evaporation strategy using a DMF solution containing equal molar quantities of PbI2, NH4I and 18-crown-6. The supramolecular perovskite was characterized by microanalysis for C, H and N elements, thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD) and single crystal X-ray diffraction techniques. DSC measurements demonstrated that 1 experiences a two-step thermotropic phase transition around 333 K and 383 K, respectively. The phase transition is relevant to the disorder–order transformation of the 18-crown-6 molecule at ∼333 K, while both breaking-symmetry and ordered-disordered transformation of the 18-crown-6 molecule occurred at ∼383 K. In addition, the sharp change of the PbI6 coordination octahedron distortion degree plays a synergistic role in the two-step phase transition. The dielectric relaxation occurs above 243 K in 1 and is mainly attributed to the displacement of the NH4+ ions relative to the ring of the 18-crown-6 molecule and {PbI3}∞ chain induced by an AC electrical field. [ABSTRACT FROM AUTHOR]

The supramolecular lead iodide perovskite crystals, {[NH4(18-crown-6)]PbI3}∞ (1), (18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane), was successfully achieved by a facile solvent evaporation strategy using a DMF solution containing equal molar quantities of PbI2, NH4I and 18-crown-6. The supramolecular perovskite was characterized by microanalysis for C, H and N elements, thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD) and single crystal X-ray diffraction techniques. DSC measurements demonstrated that 1 experiences a two-step thermotropic phase transition around 333 K and 383 K, respectively. The phase transition is relevant to the disorder–order transformation of the 18-crown-6 molecule at ∼333 K, while both breaking-symmetry and ordered-disordered transformation of the 18-crown-6 molecule occurred at ∼383 K. In addition, the sharp change of the PbI6 coordination octahedron distortion degree plays a synergistic role in the two-step phase transition. The dielectric relaxation occurs above 243 K in 1 and is mainly attributed to the displacement of the NH4+ ions relative to the ring of the 18-crown-6 molecule and {PbI3}∞ chain induced by an AC electrical field. [ABSTRACT FROM AUTHOR]

Lead halide perovskite materials are promising candidates for the application of semitransparent solar cells due to their bandgap tunability and high device efficiencies. The high absorption coefficient of these materials, however, makes it difficult to attain high average visible transmittance values without compromising the power conversion efficiencies (PCEs). In this work, a co‐evaporation process is employed to fabricate thin (50 and 100 nm) methylammonium lead iodide (MAPI) perovskite films and integrate them in semitransparent perovskite solar cells (ST‐PSCs). Due to the compact nature of the thin MAPI films, the resultant fully vacuum and room temperature‐processed devices demonstrate high fill factor values approaching 80% and open‐circuit voltage values close to 1100 mV. As a result of this, the ST‐PSCs exhibit PCE's as high as 9% with a photopic average visible transmittance of the full device of 23%. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have been the promising stars in the solar cell industry for dramatically improving the power conversion efficiency (PCE) in the past decade and reaching a record over 25%. However, there are still many issues to be solved on an industrial scale. One of these challenges is the material stability of precursors, which may significantly affect the performance of PSCs. Herein, a facile method is provided to produce controllable lead iodide as the raw material for formamidinium‐based PSCs whose performance is highly correlated to the crystallographic‐preferred orientation of PbI2. The PSCs based on the PbI2 synthesized at 120 °C exhibit the best PCE of 17.96% among these solar cells. Furthermore, the perovskite solar module with an active area of 3.68 cm2 and a PCE of 16.08% is successfully demonstrated, showing the potential of scaling up in the future. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) were fabricated using a two-step spin-coating method with MACl added to the inorganic layer. The properties of the perovskite films were characterized by SEM, XRD, PL, UV-vis spectra, etc. The morphology of the PbI2 film was significantly changed, and the formation of MACl-related intermediate phase was observed at the grain boundaries. The grain size and crystallinity of the perovskite film increased, and the morphology at grain boundaries was optimized, while the composition of perovskite remained unchanged. The introduction of MACl improved the open circuit voltage ( V OC ) and fill factor (FF) of PSCs, and the optimal device efficiency reached 21.59%. This paper presents a new approach using additives in inorganic layers to optimize the crystallization process for efficient PSCs. [ABSTRACT FROM AUTHOR]

The remarkable performance of organometallic lead halide perovskites in solar cell technology has drawn attention due to their intriguing properties. Commercialization of perovskite solar cell (PSC) technology is hampered by high-cost device fabrication techniques and inadequate stability under ambient conditions. In this study, we used low-grade PbI2 to make highly stable Methylammonium lead Iodide (MAPbI3) powder via sono-chemical method, in order to reduce the cost of the PSCs. The sono-chemical method is used to synthesize MAPbI3 microcrystals because of its significant advantages, including morphological control and educt dissolution support. The tetragonal phase of the synthesized perovskite (MAPbI3) powder was confirmed using PXRD measurement. The synthesized MAPbI3 powder was then subjected to series of analysis, including UV–Vis–NIR absorption, PL Emission, FTIR and TGA. The FESEM and TEM analyses reveal that the size of synthesized MAPbI3 microcrystals is in the range of 0.3–2 μm. The optical and photovoltaic properties of conventional solution-based films and powder-based recrystallization films were studied and compared their performance in the carbon-based perovskite solar cell (C-PSC). The powder-based solar cell exhibits slightly higher power conversion efficiency (10.1%) than the device fabricated by conventional solution-based approach (9.5% for high-grade PbI2 + MAI and 6.8% for low-grade PbI2 + MAI). The enhanced photovoltaic characteristics of the recrystallization-based devices were attributed to the homogeneous perovskite film with large grain size and high crystalline properties. [ABSTRACT FROM AUTHOR]

Excess PbI2 in perovskite film is an effective strategy for boosting perovskite solar cells (PSCs) performance. However, the presence of unreacted PbI2 is a critical source of intrinsic instability in perovskite under illumination, due to the photolysis of PbI2 (decomposed into metallic lead and iodine). Herein, this issue is solved by applying ionic liquids (ILs) on PSCs where the ILs can form types of stable supramolecules with residual lead iodide. The formation process and mechanism of the supramolecules are elucidated. The residual PbI2 is also revealed to cause high level lead interstitial defects and induced tensile strain which further deteriorate device performance. The self‐assembled supramolecular complex can passivate the PSCs where significant enhancements are achieved in both power conversion efficiency (PCE, from 21.9% to 23.4%) and device stability (retaining 95% of the initial PCE after 4080 h in ambient dry‐air storage, and 80% after 1400 h continuous light illumination). [ABSTRACT FROM AUTHOR]

Inorganic perovskite cesium lead iodide nanocrystals (CsPbI3 NCs) are good candidates for optoelectronic devices because of their excellent properties of remarkable luminous performance (high luminous efficiency, narrow luminous spectral line), and high photoelectric conversion efficiency by using simple preparation method. But their inherent poor stability greatly limits its practical applications. In this paper, electrospinning is used to grow fibrous membranes with embedded cesium lead iodide perovskite nanocrystals (PNCs) formed in situ in a one-step process. It was found that cubic α -CsPbI3 PNCs were formed in polymer fibers, showing bright and uniform fluorescence signals. Furthermore, the water wetting angles were increased by the fibrous structure enhancing the hydrophobicity and the stability of the fibrous membranes in water. The electrospun fibrous membrane containing CsPbI3 was combined with another membrane containing CsPbBr3 under a blue light-emitting diode (LED) to create a white LED (WLED) in air successfully with CIE coordinates (0.3020, 0.3029), and a correlated color temperature of 7527 °K, indicating high purity of WLED. Our approach provides a new way to create highly stable, photoluminescent water-resistant perovskite nanocrystalline films. [ABSTRACT FROM AUTHOR]

Organic–inorganic lead halide perovskite is promising photovoltaic energy harvesting material to fabricate high-efficiency solar cells. To enhance the power conversion efficiency (PCE) and stability of the fabricated device, a high-quality, pinhole-free, and larger grain size perovskite film is essential. Anti-solvent-assisted crystallization is a popular technique to deposit perovskite thin film. With the help of this technique, perovskite layer can be deposited with smooth surface morphology, low surface defect density, and excellent carrier transport. However, choosing a proper anti-solvent is essential for highly efficient perovskite solar cells (PvSCs). Here, we qualitatively evaluate the impacts of different anti-solvent on methylammonium lead iodide (MAPbI3) perovskite film. We used chlorobenzene (CB), diethyl ether (Eth), toluene (TL), and isopropyl alcohol (IPA) as an anti-solvent. Our result demonstrates that the anti-solvent with a relatively higher boiling point and lower polarity contributes to superior efficiency, low hysteresis, and better reproducibility of MAPbI3 active layer-based PvSCs. The device fabricated with CB anti-solvent exhibits the best PCE of 8.16% with a Cu-based electrode. This work provides a promising approach to controlling the growth and morphology of perovskite films and paves the way for further optimizing the fabrication process of large-area low-cost electrode-based high-efficiency devices. [ABSTRACT FROM AUTHOR]

Summary: The presence of intrinsic defects in the bulk perovskite absorber and recombination of charge carriers hampers the device performance in perovskite solar cells. To overcome the bulk defects in the formamidinium cesium lead iodide (FACsPbI3) perovskite absorber layer, A‐site cation engineering using nitrogen containing heterocyclic aromatic monovalent molecule, glyoxaline iodide/imidazolium iodide (IAI) is carried out successfully in this study. Even though IAI is a relatively larger aromatic cation, an optimized concentration of co‐doping in FACsPbI3 does not destroy the 3D perovskite lattice as evidenced by X‐ray diffraction analysis. Binding energy of Pb‐4f core‐level shifts to lower energy that reveals that the free lone pair of electrons on the nitrogen atom in IAI binds with the undercoordinated Pb2+, which results in in situ defect passivation. As a result, the in situ passivated device shows reduced trap filled limit voltage (VTFL) of 0.09 V (from 0.19), lower trap state density (~1.05 × 1015 cm−3), and reduced diode ideality factor (nid) of 1.36 from 1.48. Due to the reduced nonradiative recombination an increased trap‐assisted lifetime of 410 ns was also observed compared to the bare device (177 ns). The lower theoretical open circuit voltage (VOC) loss with enhanced theoretical fill factor (FF0) reveals that the incorporation of third A‐site cation results in reduced charge carrier transport loss. Finally, the in situ passivated device shows 60 mV higher open‐circuit voltage (VOC) than the bare device (1.01‐1.07 V) with enhanced fill factor, which leads to an improved power conversion efficiency of 16.02%. The findings reported here demonstrate the beneficial role of the third A‐site cation in passivating the inherent defects seen in formamidinium cesium lead iodide absorber. [ABSTRACT FROM AUTHOR]

The incorporation of black phosphorus (BP) into methylammonium lead iodide (MAPbI3) perovskites has been investigated and optimized by a high throughput screening method using scanning photoelectrochemical microscopy (SPECM) to determine how the addition of BP affects its photoelectrochemical and photovoltaic properties. An optimum ratio of 2.0 mole% BP/MAPbI3 perovskite composite generates an increased photocurrent response compared to pristine MAPbI3 for 2 mM benzoquinone (BQ) reduction at −0.6 V vs Ag/AgNO3 on a spot array electrode under illumination. Due to the relatively high quantum yield of MAPbI3, time-resolved photoluminescence measurements have been conducted to investigate photophysical behaviors of BP/MAPbI3 composites. The optimal 2.0 mole% BP/MAPbI3 exhibits an increased electron-hole diffusion lifetime compared to the pristine MAPbI3 perovskite. Finally, we demonstrate the enhanced efficiency and stability of 2.0% BP/MAPbI3-based perovskite solar cells arising from impeded Pb0-defect generation and suppressed charge-carrier recombination. [ABSTRACT FROM AUTHOR]

Interfaces between hybrid perovskite absorber and its adjacent charge‐transporting layers are of high importance for solar cells performance. Understanding their chemical and electronic properties is a key step in designing efficient and stable perovskite solar cells. In this work, the tapered cross‐section photoemission spectroscopy (TCS‐PES) method is used to study the methylammonium lead iodide (CH3NH3PbI3) (MAPI)‐based solar cells in two configurations, that is, in an inverted p–i–n and in a classical n–i–p architecture. It is revealed in the results that the MAPI film deposited once on the n‐type TiO2 and once on the p‐type NiOx substrates is neither an intrinsic semiconductor nor adapts to the dopant nature of the substrate underneath, but it is heavily n‐type doped on both substrates. In addition to that, the TCS‐PES results identify that the band bending between the MAPI film and the hole transporting layer (HTL) layer depends on the perovskite solar cells architecture. In particular, a band bending on the HTL side in the n–i–p and at the MAPI in the p–i–n architecture is found. The flat band of NiOx at the NiOx/MAPI interface can be explained by the Fermi level pinning of the NiOx at the interface. [ABSTRACT FROM AUTHOR]

Formamidine lead iodide (FAPbI3) perovskite material is very suitable for solar photovoltaic devices because of its ideal low band gap, theoretically high efficiency, and wide range of solar spectral absorption, coupled with its good thermal stability. A two-step spin coating method could control the crystallization process of formamidine lead iodide perovskite films better, resulting in more easily repeatable high-quality films. However, it is still difficult to avoid the formation of halide I-vacancy during the preparation of films, which will affect device performance and stability. In this paper, we added small molecular formamidine formate (FAHCOO) into the PbI2 precursor solution. Due to the high binding energy between HCOO− and I-vacancy, film defects caused by I-vacancies could be passivated. A molecular exchange process could be introduced in the two-step method with the addition of FAHCOO. The exchange process could delay the crystallization process in perovskite films and make them transform more fully; thus, ultimately improving the crystallization quality of the films. In addition, by adding FAHCOO to the PbI2 precursor solution, a small number of FAPbI3 can be pre-generated as templates. These templates could induce the growth of specific crystal planes of FAPbI3 in the second step reaction; thereby, improving the crystallinity of FAPbI3 films. The FAPbI3 of devices with optimized FAHCOO show a champion power conversion efficiency (PCE) of 19.04%, apparently higher than that of the controlled devices without FAHCOO (16.69%). For working stability tests under AM 1.5G illumination in an air environment, PSCs with FAHCOO showed nearly 100% of their initial efficiency after a 4100 s tracking test, while the original control device dropped to about 94%. [ABSTRACT FROM AUTHOR]

Lead halide 2D hybrid perovskites (HP) have emerged as promising materials for photovoltaic and lighting applications. Solvent‐free preparations offer greener route, but require congruent melting of halide perovskite for thin films, which has been demonstrated only for monolayered HP (n=1 of the (A)2(MA)n−1PbnI3n+1 series) at the quite high temperature Tm (Tmelting) of 171 °C. Here, we report on the solvent‐free preparation (n=2, 4), thermal behaviour and melt‐processed thin films of a series of HP (GABA)2(MA)n−1PbnI3n+1 (n=1, 2, 4; GABA+: 4‐ammoniumbutyric acid cation). The n=1 and n=2 HP have an exceptional low congruent Tm of 126 °C and 136 °C, respectively, and, for n=1, a very good stability in the molten state. The liquid–solid reaction of molten (GABA)2PbI4 or (GABA)2(MA)Pb2I7 with MAPbI3 in 1/1 (T=130 °C) or 1/2 (T=135 °C) ratio leads to pure phases of the n=2 HP and (GABA)2(MA)3Pb4I11 (n=4, Tm=185 °C), respectively. Melt‐processed thin films of n=1, n=2 and n=4 HP have also been prepared. [ABSTRACT FROM AUTHOR]

Recently, metal halide perovskites have attracted considerable interest as highly emissive phosphors for use in white light‐emitting diodes (WLEDs). In perovskites, the migration of halide anions between green‐emitting bromide (e.g., CsPbBr3) and red‐emitting iodide (e.g., CsPbI3) materials is one obstacle to application. Here perovskite WLEDs that do not suffer from the anion exchange problem are reported: this is done by developing green‐emitting single‐layer sheets of (RNH3)2PbI4 (R = C18H35–, C12H25–, and C8H17–) and uniting these with red‐emitting CsPbI3 perovskite quantum dots (QDs). It relies on self‐assembly from ligand‐capped CsPbI3 nanocrystals to form single‐layer sheets of (C18H35NH3)2PbI4: via judicious selection of alkylamines and alkyl acids, (RNH3)2PbI4 single‐layer sheets that exhibit bright and stable green emission with well‐defined single‐layer thickness are produced. Emission from 505, 512 to 536 nm is tuned and a narrow (<20 nm) linewidth is retained. Perovskite LEDs that produce white light with chromaticity coordinates (0.32, 0.33) and color gamut that reaches 117% National Television System Committee (NTSC) in the International Commission on Illumination (CIE) 1931 color space are demonstrated. [ABSTRACT FROM AUTHOR]

Combining the characteristics of hybrid perovskites and layered materials, 2D Ruddlesden–Popper perovskites exhibit unique properties, some of which still require to be deeply understood. In this study, the vibrational signatures of such materials are analyzed by collecting experimental Raman spectra of four distinct compounds. Supported by density functional theory simulations, the role of the phenyl spacer single fluorination on the phonon modes of two similar yet different compounds, i.e., phenethylammonium lead iodide (PEAI) and 4‐fluorophenethylammonium lead iodide (PEAI‐F), is explained. In addition, this work analyzes some so‐far unreported experimental Raman peaks in the 600–1100 cm−1 range and discusses their origin in this class of 2D compounds. This work paves the way for a better design of novel compounds as well as for their exploitation in (opto)electronic applications. [ABSTRACT FROM AUTHOR]

Metal‐halide perovskites (MHPs) have made incredible achievements in the past few years, especially in the area of perovskite light‐emitting diodes (PeLEDs). Nevertheless, hole transport layers (HTLs) used in most highly efficient PeLEDs usually have low hole mobilities in the range of 10−4–10−6 cm2 V−1 s−1, much lower than that of MHPs, resulting in severe roll‐off and low radiance of the devices. Here, methylammonium lead iodide (MAPbI3) is successfully deposited on top of methylammonium lead chloride (MAPbCl3) using orthogonal solvent to form heterojunction PeLEDs (HJ‐PeLEDs). Due to the high hole mobility of MAPbCl3 ≈42 cm2 V−1 s−1, the HJ‐PeLEDs exhibit a peak external quantum efficiency of 10.7% and a high radiance of 157 W sr−1 m−2 at a low applied voltage of 3.9 V. Furthermore, the large‐area (28 cm2) HJ‐PeLEDs made by blade coating shows a uniform and high radiance of ≈180 W sr−1 m−2. This work provides a novel strategy to fabricate bright and large‐area PeLEDs to meet the requirements of commercial applications. [ABSTRACT FROM AUTHOR]

Methylammonium lead iodide, as related organometal halide perovskites, emerged recently as a particularly attractive material for photovoltaic applications. The origin of its appealing properties is sometimes assigned to its potential ferroelectric character, which remains however a topic of intense debate. Here, we rationalize from first-principles calculations how the spatial arrangement of methylammonium polar molecules is progressively constrained by the subtle interplay between their tendency to bond with the inorganic framework and the appearance of iodine octahedra rotations inherent to the perovskite structure. The disordered tetragonal phase observed at room temperature is paraelectric. We show that it should a priori become ferroelectric but that iodine octahedra rotations drive the system toward an antipolar orthorhombic ground state, making it a missed ferroelectric. [ABSTRACT FROM AUTHOR]

Interfaces composed of three-dimensional (3D) and 2D organic–inorganic hybrid formamidinium lead iodide (FAPbI3) linked by organic spacers (OSs) are studied using first-principles calculations. The OS cations with aromatic rings, like phenylethylammonium and anilinium (AN), are found to be more favourable for enhancing the stability of the 3D/2D interface than butylammonium with aliphatic chains. The AN-based interface shows the highest resistance to penetration of water molecules. [ABSTRACT FROM AUTHOR]

Perovskites have been in the spotlight in the field of solar cells due to their high efficiency and their low cost of materials and fabrication processes. Perovskite solar cells (PSCs) have shown an efficiency of up to 25%. Nevertheless, PSCs have some drawbacks such as rapid degradation in ambient conditions. To improve PSC stability, lead is usually replaced with bismuth. In this article, we report the results when doping the methylammonium lead iodide (CH3NH3)PbI3, aka MAPbI3, with different bismuth quantities. The incorporation of bismuth into the lattice leads to a remarkable change in optoelectronics and morphological structure. Substituting lead atoms with 2% bismuth improves some characteristics of MAPbI3 layers, such as removing pinholes and increasing crystallite size and optical absorption. Furthermore, bismuth doping improves the stability of pure MAPbI3 layers, which after 4 weeks exhibits higher degradation compared to bismuth-doped MAPbI3 samples, which remain stable after that period. [ABSTRACT FROM AUTHOR]

Among perovskites, the research on cesium lead iodides (CsPbI3) has attracted a large research community, owing to their all-inorganic nature and promising solar cell performance. Typically, the CsPbI3 solar cell devices are prepared at various heterojunctions, and working at fluctuating temperatures raises questions on the material stability-related performance of such devices. The fundamental studies reveal that their poor stability is due to a lower side deviation from Goldschmidt's tolerance factor, causing weak chemical interactions within the crystal lattice. In the case of organic–inorganic hybrid perovskites, where their stability is related to the inherent chemical nature of the organic cations, which cannot be manipulated to improve the stability drastically whereas the stability of CsPbI3 is related to surface and lattice engineering. Thus, the challenges posed by CsPbI3 could be overcome by engineering the surface and inside the CsPbI3 crystal lattice. A few solutions have been proposed, including controlled crystal sizes, surface modifications, and lattice engineering. Various research groups have been working on these aspects and had accumulated a rich understanding of these materials. In this review, at first, we survey the fundamental aspects of CsPbI3 polymorphs structure, highlighting the superiority of CsPbI3 over other halide systems, stability, the factors (temperature, polarity, and size influence) leading to their phase transformations, and electronic band structure along with the important property of the defect tolerance nature. Fortunately, the factors stabilizing the most effective phases are achieved through a size reduction and the efficient surface passivation on the delicate CsPbI3 nanocrystal surfaces. In the following section, we have provided the up-to-date surface passivating methods to suppress the non-radiative process for near-unity photoluminescence quantum yield, while maintaining their optically active phases, especially through molecular links (ligands, polymers, zwitterions, polymers) and inorganic halides. We have also provided recent advances to the efficient synthetic protocols for optically active CsPbI3 NC phases to use readily for solar cell applications. The nanocrystal purification techniques are challenging and had a significant effect on the device performances. In part, we summarized the CsPbI3-related solar cell device performances with respect to the device fabrication methods. At the end, we provide a brief outlook on the view of surface and lattice engineering in CsPbI3 NCs for advancing the enhanced stability which is crucial for superior optical and light applications. [ABSTRACT FROM AUTHOR]

Lead halide perovskites are semiconductor materials which are employed as nonintentionally doped absorbers inserted between two selective carrier transport layers (SCTL), realizing a p‐i‐n or n‐i‐p heterojunction. In our study, we have developed and investigated a lateral device, based on methylammonium lead iodide (MAPbI3) in which the p‐i‐n heterojunction develops in the horizontal direction. Our research suggests that the effective doping level in the MAPbI3 film should be very low, below 1012 cm−3. Along the vertical direction, this doping level is not enough to screen the electric field of the buried heterojunction with the SCTL. The perovskite work function is therefore affected by the work function of the SCTL underneath. From drift‐diffusion simulations, we show that intrinsic perovskite‐SCTL structures develop mV range surface photovoltages (SPVs) under continuous illumination. However, perovskite‐SCTL structures can develop SPVs of hundreds of mV, as confirmed by our measurements. We therefore analyzed the compatibility between low doping and low defect densities in the perovskite layer and such high SPV values using numerical modeling. It is shown that these high SPV values could originate from electronic processes due to large band offsets in the buried perovskite‐SCTL heterojunctions, or at the SCTL‐transparent conductive oxide (TCO) buried heterojunction. However, such electronic processes can hardly explain the long SPV persistence after switching off the illumination. [ABSTRACT FROM AUTHOR]

The short lifetime of perovskite solar cell devices limits the application of the technique, which is yet to be resolved, despite many attempts. An important step is made here by the numerical modelling method, which reveals the decomposition kinetics under the protection of halogen bonds from excess PbI2. Irregular diffusion behaviour of water molecules is observed when excessive PbI2 is introduced, possibly due to the passivation and hindrance from the halogen bond, resulting in a lifetime enhancement of at least five times. The detailed kinetics are also obtained by analyzing the decomposition rate curve, offering a possible path towards high-stability PCE perovskite solar devices, by increasing the PbI2 concentration to above the threshold, which opens an unprecedented route in perovskite solar cell research, and is, hopefully, of intrinsic interest to the broad materials research community as well. [ABSTRACT FROM AUTHOR]

[Display omitted] • For the first time, the correlation between working pressure and the properties of sputtered PbI 2 is demonstrated. • The re-sputtering of iodine depends on the working pressure. • Lower working pressure increases the iodine vacancy defects in the film, resulting in the formation of metallic lead. • We propose a structure model of sputtered PbI 2 depending on the working pressure. Radio frequency (RF) magnetron sputtering is a vapor deposition technique known for its good step coverage, high material utilization, and industrial adaptability. However, its application in the deposition of lead iodide (PbI 2), a key semiconductor in photovoltaic applications, has been underexplored. In this study, for the first time, the correlation between working pressure and film properties is demonstrated. The formation of metallic lead and severe iodine deficiency, reported as a flaw of sputtered PbI 2 films, is revealed to occur at low working pressure around 2 mTorr. Increasing the pressure suppresses the re-sputtering of iodine, manipulating the properties of the films. As working pressure increases to 25 mTorr, the metallic lead diminishes and the atomic ratio (I/Pb) changes from 0.8 to 1.8. Thus, we propose a structure model of sputtered PbI 2 depending on the working pressure, demonstrating that adjusting the pressure eliminates the previously reported drawbacks of sputtered films while maintaining a conformal coating. Moreover, we are the first to report that sputtered PbI 2 can be converted into perovskite through the close-spaced sublimation. We believe this study will pave a way for accelerating research on the fabrication of PbI 2 films via RF magnetron sputtering, a field with significant potential in industrial application. [ABSTRACT FROM AUTHOR]

Time-resolved microwave conductivity (TRMC) is a highly versatile method to rapidly evaluate the electronic properties of semiconducting compounds without the need to construct and optimize electronic devices. In this report, we study how bimolecular and Auger recombination mechanisms affect TRMC measurements. In particular, we investigate how recombination reduces the measured value of the TRMC figure-of-merit: ∅∑μ, at a high incident optical fluence. Using a numerical model, we calculate how these higher-order recombination processes reduce experimentally measured values of ∅∑μ relative to a regime of low carrier concentration with little recombination. By fitting this model to experimentally obtained data for the hybrid halide perovskite compound, methylammonium lead iodide, we are able to extract the bimolecular and Auger rate constants and provide a clear determination of the sum of the hole and electron mobilities for these films. [ABSTRACT FROM AUTHOR]

The effects of soft X-ray exposure on structures of CH3NH3PbI3 perovskite were investigated using an X-ray photoelectron spectroscopy (XPS) time-dependent measurement method. A crystalline sample was fabricated with the inverse-temperature crystallization method. The time evolutions of the core-level and valence-band spectra were recorded to determine the compositional ratios and valence band electronic structure of the sample, respectively. In addition, first-principles calculations were conducted to evaluate the valence band XPS spectra. The in situ XPS analysis combined with theoretical calculations demonstrated a degradation of the surface of CH3NH3PbI3 perovskite into PbI2 owing to the evaporation of methylammonium iodide. [ABSTRACT FROM AUTHOR]

Hybrid halide perovskite (HHP) materials have been rigorously explored since last decade specially for their potential use as absorber layer material in perovskite solar cells. Formamidinium (FA) based HHP materials show many fascinating properties and exhibit thermal stability. However, photoactive cubic phase of formamidinium lead iodide (FAPbI 3) material is unstable at room temperature. To overcome the phase stability issue, substitution of Cs+ or MA+ (methylamine) ion has been found useful. Further, to enhance the material properties of FA-MA or FA-Cs based HHP materials, alkali ion doping is widely explored. In this study, the role of K+ ion doping in enhancing the optoelectronic properties of Cs-FA based HHP material is studied thoroughly by structural and optical characterizations. The XRD results show the suppression of yellow non-perovskite phase after Cs doping in FAPbI 3 material. The SEM results predict increased grain size with small K+ content in Cs 0.1 FA 0.9 PbI 3 material. The PL and TRPL results predict the increase in radiative recombination and charge carrier lifetime with small K-doping and detrimental effects of doping concentration above 3 % of K. The solar cell simulation results yield a maximum power conversion efficiency of 18.21 % in K 0.03 (Cs 0.1 FA 0.9) 0.97 PbI 3 absorbing layer-based device. • The suppression of yellow non-perovskite phase with Cs-doping in FAPbI 3 material is observed. • K co-doping is beneficial for enhancing particle size but large K-amount yields degradation. • Enhanced PCE in K x (Cs 0.1 FA 0.9) 1-x PbI 3 (x = 3 %) based device is due to the variation in carrier lifetime and absorbance. [ABSTRACT FROM AUTHOR]

This study employed time-of-flight secondary ion mass spectrometry (TOF-SIMS) to investigate degradation pathways at the nanoscale, utilizing its capacity for in-depth chemical and structural analysis through various methods, including depth profiling and 3D analysis. A key focus is the matrix effect in ToF-SIMS, which alters secondary ion yields based on the sample matrix composition, influencing species identification and quantification. We show that this effect can be used to enhance the resolution of ToF-SIMS beyond its traditional limits, allowing for detailed imaging of the degradation process. Our findings indicate that the initial formation of PbI 2 phases, a crucial step in the degradation pathway triggered by environmental factors, can be traced and visualized. By investigating the sputtering yields and secondary ion formation, we reveal the nonlinear sputtering regimes present in MAPI, contributing to our understanding of the mechanisms driving perovskite degradation. The application of this enhanced analytical technique paves the way for improved degradation studies. • The formation of secondary ions in MAPI sputtering is through a bond-breaking mechanism. • Quantitative SIMS analysis of MAPI is still impossible. • 3-D analysis of MAPI by TOF-SIMS provide information about degradation mechanism. • SIMS matrix effect offers visualization of PbI 2 crystallites with size less than lateral resolution. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) with solution-based fabrication processes deserve a simple and controllable fabrication process to produce cost-effective new-generation solar cells. Increasing optoelectrical properties of the light-harvesting perovskite layer during the fabrication process is used to enhance photovoltaic efficiency and the stability of PSCs. Here, ellagic acid was added into the lead iodide precursor to control the reaction of lead iodide with formamidinium iodide to generate a perovskite layer with enlarged grains. The obtained results showed the ellagic acid additive reduced charge recombination losses within solar cells and prompted charge transfer from perovskite to electron transporting layer and hole transporting layer, recording a champion efficiency of 22.04 % along with an open circuit voltage of 1.095 V, short-circuit current density of 24.17 mA cm−2, and fill factor of 78.94 %. In addition, the ellagic acid-based PSCs showed considerable stability improvement against the humidity and light irradiance compared to the control PSCs. It can be concluded that the ellagic acid additive may push the PSCs further to commercialization. • Introduction of ellagic acid (EA) into the lead iodide precursor enhances the optoelectrical properties of the perovskite layer, resulting in a champion efficiency of 22.04 % for Perovskite solar cells (PvKSCs). • EA additive reduces charge recombination losses within PvKSCs and facilitates efficient charge transfer, contributing to improved photovoltaic performance. • EA-based PvKSCs demonstrate substantial stability improvements against humidity and light irradiance, making them a promising candidate for commercialization in the solar cell industry. [ABSTRACT FROM AUTHOR]

In this study, perovskite solar cells (PSCs) were fabricated using a two-step solution deposition method. A laser beam was applied at the interface between lead iodide (PbI 2) and methylammonium iodide to change the reaction temperature and stimulate the growth of perovskite crystals. A notable enhancement was observed in the power conversion efficiency of PSCs. The laser scanning speed was investigated to control the reaction temperature and further control the crystallization and morphology of the perovskite film. Based on the optimized laser scanning speed, the best and average PCEs obtained were 14.33 % and 13.92 ± 0.52 %, respectively, which were higher than those achieved using the conventional technique (12.18 % and 11.37 ± 0.74 %, respectively) and the conventional heating methods (14.09 % and 13.28 ± 0.56 %, respectively). The optimal reaction temperature at the interface was predicted to be 80 °C under optimized conditions using the COMSOL software. This study will help in scaling this technique for large–area PSCs, optimizing the laser parameters for different perovskite compositions, and investigating the long-term stability of enhanced PSCs, boosting their commercial viability. [Display omitted] • Laser-induced heat treatment helps to control the reaction temperature. • Laser treatment enhances morphology and crystallinity of perovskite films. • Optimized reaction temperature of 80 °C achieved best PCE of 14.33 %. • PCE enhancement by 22 % compared to normal heating method. [ABSTRACT FROM AUTHOR]

The study discussed in this publication aimed to develop a perovskite solar cell adapted to operating conditions at reduced temperature and pressure and less than 1 μm thick. The physical vapor co-deposition technique was proposed and successfully used to create a solar cell structure with a thin layer of hybrid perovskite as an energy-collecting material. A comprehensive analysis of methylammonium lead iodide behavior in a wide temperature range from 10 K to 320 K was carried out to implement this project. The initial phase included assessing the degradation of the perovskite material layer after cooling to the temperature of liquid helium and then re-heating it to room temperature. Then, using spectroscopic techniques, the characteristics of the layers' optical and electrical properties were determined. The obtained results allowed the design of the complete structure of a thin-film perovskite cell, which was made using only the vacuum sublimation process. Simulations using the SCAPS-1D program and experimental results showed high agreement and allowed for obtaining an efficiency of approximately 18.5 % in the interested temperature range. Perovskite solar cell stability tests over six months confirmed the positive impact of the proposed technique for depositing the complete cell structure on its temporal stability. The research results are optimistic for the applications of perovskite cells in space. • Innovative physical vapor co-deposition technique for hybrid perovskite solar cells. • Low-temperature characterization of photo-electro-physical parameters for MAPbI 3 thin films. • Comparative performance analysis of solar cells based on hybrid perovskite. • Design and implementation of PSC with constant efficiency over a wide temperature range (10–300 K). • High temporal stability of PSC with a photoactive layer made in the PVco-D process. [ABSTRACT FROM AUTHOR]

Electrospray deposition technique has been reported previously for fabricating effective and stable perovskite thin film, leading to efficient perovskite solar cells. In this work, a comprehensive investigation of the formation mechanism of methylammonium lead iodide perovskite (CH 3 NH 3 PbI 3) film by electrospray technique is demonstrated and compared to the formation mechanism through the conventional spin coating technique. In the electrospray process, charged MAI nanoparticles are gradually introduced onto the PbI 2 film, intercalating within the PbI 2 structure to produce the perovskite film. In contrast, the spin-coating method involves supplying the MAI solution in bulk, leading to perovskite crystal formation through the dissolution of the PbI 2 layer by the MAI solution, followed by recrystallization into perovskite oriented in the [110] direction, 30° inclined to the substrate. The impact of charge and the electric field on the formation of perovskite film using the electrospray is explored. Furthermore, the intrinsic stability of perovskite films is monitored in real-time in a highly humid environment (≥80 % relative humidity (RH)) using in-situ Grazing Incidence Wide Angle X-ray Scattering (GIWAXS), and a degradation mechanism is proposed to enhance the durability of the perovskite-based devices. The study further delves into the comparison of the stability of electrosprayed and spin-coated perovskite film, and the impact of humidity level and the presence of a hole-transporting layer on the stability of the perovskite layer. Overall, this work provides a detailed understanding of the formation and humidity-induced degradation mechanism of electrosprayed perovskite films, offering insights that can extend to various applications of perovskite materials. [Display omitted] • Formation mechanism of CH 3 NH 3 PbI 3 perovskite using electrospray is described and compared to the spin-cated perovskite. • In electrospray, perovskite formation occurs through CH 3 NH 3 I intercalation into PbI 2 film • In spin coating, formation occurs through dissolution recrystallization. • CH 3 NH 3 PbI 3 perovskite degrades through the formation of perovskite hydrate leading to form lead iodide. • Electrosprayed perovskite is highly stable compared to spin-coated perovskite. [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrid perovskite nanomaterials hold immense potentials for photovoltaic and optoelectronic devices, while their structural instability under external stimuli has seriously impeded their practical applications. Meanwhile, the microscopic understanding of structural degradation mechanisms for these low-dimensional perovskite nanomaterials remains incomplete. Herein, we report the degradation mechanisms on surface of perovskite methylammonium lead iodide (MAPbI 3) nanowires under electron-beam irradiation by in situ transmission electron microscopy. Our atomic-scale study has directly identified the decomposition of MAPbI 3 and the subsequent growth of PbI 2 nanocrystals are highly anisotropic. Furthermore, PbI 2 nucleation follows the heterogeneous two-step mechanism with the growth kinetically controlled by the coherent MAPbI 3 /PbI 2 interface. [Display omitted] • The surface degradation pathway of MAPbI 3 nanowires is microscopically revealed. • The facet-dependent degradation of MAPbI 3 induces anisotropic growth of PbI 2. • A non-classical two-step nucleation mechanism is identified for PbI 2 nanocrystals. • The coherent interface of MAPbI 3 /PbI 2 is critical for the structural transition. [ABSTRACT FROM AUTHOR]

In halide perovskite solar cells the formation of secondary-phase excess lead iodide (PbI2) has some positive effects on power conversion efficiency (PCE) but can be detrimental to device stability and lead to large hysteresis effects in voltage sweeps. We converted PbI2 into an inactive (PbI2)2RbCl compound by RbCl doping, which effectively stabilizes the perovskite phase. We obtained a certified PCE of 25.6% for FAPbI3 (FA, formamidinium) perovskite solar cells on the basis of this strategy. Devices retained 96% of their original PCE values after 1000 hours of shelf storage and 80% after 500 hours of thermal stability testing at 85°C. [ABSTRACT FROM AUTHOR]

Solution processing of perovskite solar cells (PSCs) is highly promising for the high‐throughput production of cost‐effective devices. Although PSCs have achieved great advances in power conversion efficiency, challenges still remain in the reproducibility of high‐quality perovskite thin film with simultaneously improved precursor solution stability. Here, a reactive inhibition strategy by introducing diethyl (hydroxymethyl) phosphonate (DHP) in perovskite precursor solution is successfully employed to improve the stability of precursor solution and the performance of corresponding device. DHP inhibits the reactivity of the iodide and formamidinium ions through multiple chemical bonds, ensuring the stability of the precursor solution. In addition, due to chelation interaction of Pb2+ with the oxygen of PO in DHP, the DHP in the perovskite film improves the film quality with desired stoichiometry by reducing the defects and the content of lead iodide. The DHP‐doped precursor solution and corresponding devices show excellent performance reproducibility and super stability under ambient conditions for more than 50 days, which illustrates the commercial feasibility for scalable fabrication. [ABSTRACT FROM AUTHOR]

The conductivity of 2D perovskite is mainly dominated by halide metal octahedron skeletons. However, in contrast to 3D perovskite structures, the layered inorganic skeletons are easily compressed or stretched by large organic cations, causing serious microstrain with impaired optoelectronic responses. Here, fluorination modulated supramolecular interactions in 2D fluorophenethylammonium lead iodide (FPEA2PbI4) perovskites are reported. In the double layered organic spacer, interlayer supramolecular interactions between electronegative F atoms and electron‐rich benzene rings dominate the lattice microstrain of 2D (p‐FPEA)2PbI4 perovskite, which can be released by interlayer interactions pulling during compressively bending the flexible devices. This strong electrostatic interaction can maximally release the compression to the inorganic octahedron skeleton during compressive bending, leading to a maximum degree of released microstrain with improved stability. The 60% microstrain can be released by compressive bending, and the corresponding photocurrent response is recovered by about three times in (p‐FPEA)2PbI4 perovskite film. In contrast, intralayer supramolecular interactions dominate microstrain of 2D (o‐FPEA)2PbI4 perovskites, which prevents the microstrain release during compressive bending. The strong electrostatic interaction design in the organic spacer of 2D perovskite takes an important role in releasing the microstrain and re‐bursting the device performance of flexible perovskite devices. [ABSTRACT FROM AUTHOR]

Formamidinium methylammonium lead iodide (FAMAPbI3) perovskite has been intensively investigated as a potential photovoltaic material because it has higher phase stability than its pure FAPbI3 perovskite counterpart. However, its power conversion efficiency (PCE) is significantly inferior due to its high density of surface detects and mismatched energy level with electrodes. Herein, a bifunctional passivator, methyl haloacetate (methyl chloroacetate, (MClA), methyl bromoacetate (MBrA)), is designed to reduce defect density, to tune the energy levels and to improve interfacial charge extraction in the FAMAPbI3 perovskite cell by synergistic passivation of both CO groups and halogen anions. As predicted by modeling undercoordinated Pb2+, the MBrA shows a very strong interaction with Pb2+ by forming a dimer complex ([C6H10Br2O4Pb]2+), which effectively reduces the defect density of the perovskite and suppresses non‐radiative recombination. Meanwhile, the Br− in MBrA passivates iodine‐deficient defects. Consequently, the MBrA‐modified device presents an excellent PCE of 24.29%, an open‐circuit voltage (Voc) of 1.18 V (Voc loss ≈ 0.38 V), which is one of the highest PCEs among all FAMAPbI3‐based perovskite solar cells reported to date. Furthermore, the MBrA‐modified devices without any encapsulation exhibit remarkable long‐term stability with only 9% of PCE loss after exposure to ambient air for 1440 h. [ABSTRACT FROM AUTHOR]

The dissolution of lead iodide (PbI2) is very important for the purpose of avoiding environmental pollution. Here, an environmentally benign polyethylene glycol-based deep eutectic solvent (PEGylated DES) has been found to dissolve PbI2 with a 54.35% mass fraction at room temperature (25 °C), which is 716.1 times that in water (0.0759% mass fraction) at similar conditions. Furthermore, the dissolved PbI2 could be simply recycled by the addition of water as an antisolvent at room temperature. This work provides a green method for the recycling of toxic PbI2 with high performance at mild conditions. [ABSTRACT FROM AUTHOR]

Scalable thin‐film deposition methods are increasingly important for hybrid lead halide perovskite thin films. Understanding the structure evolution during non‐equilibrium processes helps to find suitable materials and processing parameters to produce films with well‐performing optoelectronic properties. Here, spin‐cast and slot‐die coated bilayers of lead iodide (PbI2) and methylammonium iodide (MAI) are investigated by in situ grazing‐incidence wide‐angle X‐ray scattering during the thermal annealing process, which converts the bilayer into methylammonium lead iodide (MAPI). Photoluminescence (PL) and UV/Vis measurements show increasing crystallinity during the annealing process and a slight PL red‐shift of the spin‐cast film, attributed to crystallite coalescence that is not prominent for the slot‐die coated film. The disintegration of the solvent‐precursor complex (MA)2(Pb3I8) ⋅ 2 DMSO and conversion into perovskite are followed in situ and differences in the morphology and time evolution are observed. In both, spin‐cast and slot‐die coated thin‐films, the isotropic orientation is dominant, however, in the slot‐die coated films, the perovskite crystallites have an additional face‐on orientation ((110) parallel to substrate) that is not detected in spin‐cast films. An Avrami model is applied for the perovskite crystal growth that indicates reduced dimensionality of the growth for the printed thin films. [ABSTRACT FROM AUTHOR]

The introduction of chirality in layered hybrid perovskites breaks the symmetry of their inorganic sub-lattices. Consequently, they show intriguing linear and non-linear optical properties. Here we explore the effect of chirality on the excitonic photoluminescence of chiral (R- and S-α-MBA)2PbI4 (MBA: methylbenzylammonium) at cryogenic temperatures. The induced chirality splits the excitonic emissions below 150 K. Additionally, (R- and S-α-MBA)2PbI4 show wavelength-tunable second harmonic generation (SHG) that depends strongly on the polarization angle of the incident light. [ABSTRACT FROM AUTHOR]

The elucidation of structure-to-function relationships for two-dimensional (2D) hybrid perovskites remains a primary challenge for engineering efficient perovskite-based devices. By combining insights from theory and experiment, we describe the introduction of bifunctional ligands that are capable of making strong hydrogen bonds within the organic bilayer. We find that stronger intermolecular interactions draw charge away from the perovskite layers, and we have formulated a simple and intuitive computational descriptor, the charge separation descriptor (CSD), that accurately describes the relationship between the Pb-I-Pb angle, band gap, and in-plane charge transport with the strength of these interactions. A higher CSD value correlates to less distortion of the Pb-I-Pb angle, a reduced band gap, and higher in-plane mobility of the perovskite. These improved material properties result in improved device characteristics of the resulting solar cells. Understanding structure-property relationships is important when designing functional materials. Here, authors propose a descriptor to help understand and predict the electronic properties of two-dimensional lead iodide perovskites for photovoltaic applications. [ABSTRACT FROM AUTHOR]

Polytriarylamine is a popular hole‐transporting materials (HTMs) despite its suboptimal conductivity and significant recombination at the interface in a solar cell setup. Having noted insufficient conjugation among the triarylamine units along the polymer backbone, we inserted a bithiophene unit between two triarylamine units through iron‐catalyzed C−H/C−H coupling of a triarylamine/thiophene monomer so that two units conjugate effectively via four quinoidal rings when the molecule functions as HTM. The obtained triarylamine/bithiophene copolymer (TABT) used as HTM showed a high‐performance in methylammonium lead iodide perovskite (MAPbI3) solar cells. Mesityl substituted TABT forms a uniform film, shows high hole‐carrier mobility, and has an ionization potential (IP=5.40 eV) matching that of MAPbI3. We fabricated a solar cell device with a power conversion efficiency of 21.3 % and an open‐circuit voltage of 1.15 V, which exceeds the performance of devices using reference standard such as poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine (PTAA) and Spiro‐OMeTAD. [ABSTRACT FROM AUTHOR]

Formamidinium lead iodide (FAPbI3) has endowed power conversion efficiencies (PCEs) up to 25.5% in regular‐structured perovskite solar cells (PSCs) because of its optimal bandgap and enhanced thermal stability. However, the performance of FAPbI3‐based inverted‐structured PSCs is unsatisfactory. Herein, four kinds of commonly used hole transport materials (HTMs) are selected, including PEDOT:PSS, PTAA, NiOx, and MeO‐2PACz, to study their impact on the methylamine chloride (MACl)‐assisted one‐step deposition of FAPbI3 films. It is found that MeO‐2PACz is the optimal substrate for stabilizing black‐phase FAPbI3 and the corresponding inverted‐structured PSCs show the best photovoltaic performance. Nonetheless, the PCE is restricted by low open‐circuit voltage (VOC) due to non‐radiative recombination caused by MACl residues. Therefore, homologous PbI2 in situ passivation is implemented to passivate defects at grain boundaries. The addition of excess PbI2 in precursor solution remarkably decreases charge trap densities and elongates carrier lifetimes. As a result, the optimized device achieves an impressive PCE of 22.13%, which is the highest efficiency of FAPbI3 based on inverted‐structured PSCs. Moreover, the best device exhibits free hysteresis and excellent long‐term stability, maintaining 92% of the initial PCEs after 800 h aging under ambient conditions. [ABSTRACT FROM AUTHOR]

In its initial phase in 2009, the inorganic‐organic hybrid perovskite solar cells (PSCs) delivered a 3.8% power conversion efficiency (PCE), which is far below the present 25.7% PCE obtained in 2022. The significant improvement of the efficiency of PSCs in such a short period has stimulated significant interest in the photovoltaic community. However, the performance of current PSCs is behind the commercially available and widely used solar cells in terms of stability and scalability. Among various commonly studied perovskite materials, methylammonium lead iodide (MAPbI3) is the most widely studied. This review will focus on the common solar cell structures (mesoporous, inverted planar p‐i‐n, planar n‐i‐p) using MAPbI3 perovskite as an active layer and the effect of these solar cell structures on their performances. Furthermore, some commonly‐used strategies are outlined for improving the device performance, such as optimizing the deposition technique of the charge transporting and the active layers, modifying the properties of the carrier transporting layer and the perovskite layer by interface engineering and doping, optimizing the perovskite surface morphology, along with others. This article will also discuss the hole transport free and electron transport free MAPbI3 PSCs. [ABSTRACT FROM AUTHOR]

Organometallic halide-based perovskite solar cells have played a significant role in the development of photovoltaic technology. The synthesis of the perovskite usually needs specific atmospheres, especially controlled humidity. Here, we demonstrate the synthesis of compact methylammonium lead iodide perovskite (MAPbI3) on TiO2 under ambient conditions through one and two-step spin-coating deposition methods, which both resulted in an unconverted PbI2 on the films. The two-step method provided a higher amount of PbI2 regarding the reaction of methyl ammonium iodide (MAI) with an outer layer of the first bonded PbI2 hindered the inner layer to interact with MAI. The Ostwald ripening (OR) process that was applied to the thin film resulted through one-step deposition synthesis has successfully converted the unformed PbI2 to MAPbI3 with a more uniform, lower void, and higher crystal size as confirmed by XRD and SEM analysis results. The application of MAPbI3 prepared using OR treatment in the solar cell resulted in higher efficiency (7.64%) than the one synthesized without OR (4.91%). [ABSTRACT FROM AUTHOR]

Metal halide perovskites are excellent semiconductors materials that can be exploited in many fields, from the vastly explored photovoltaics to the recent applications in photocatalysis. One of the material's known limitations is the poor resistance to moisture which induces degradation, triggered by the soft and defective nature of its surface. In this study, we explore non-equilibrium plasmas, to deposit a fluorocarbon polymer on the surface of a MAPbI3 film. We found that the treatment generally enhances the film stability over time, and in certain conditions it improves the perovskite optical properties, demonstrating to be a good strategy aiming defects passivation. Thanks to the solvent-free and non-invasive nature of plasmas, this technique has the potential to be extensively applied to a wide range of perovskite materials targeting different applications. [ABSTRACT FROM AUTHOR]

Thin films of methylammonium lead iodide (MAPbI3) were deposited on glass slides under various preparation conditions by a two-step dip-coating method, using dip-coated lead iodide (PbI2) thin films as the underlying layer. The dip-coating method used involved immersion of a slowly rotating substrate in the required solution. The PbI2 film was immersed into methylammonium iodide (MAI) solution in 2-propanol for 10–60 min. The MAPbI3 films were thermally annealed at 85 °C for 10–30 min. Fundamental properties of the annealed MAPbI3 films were studied by x-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet-visible spectrophotometry. The XRD patterns and SEM micrographs revealed single tetragonal-phase structure, with diffraction peaks became intense and narrow with increasing dipping times and upon thermal annealing. Transmittance spectra of these MAPbI3 film/glass systems declined steeply near 780 nm , equivalent to a bandgap energy of 1.55 eV , assigned to the MAPbI3 with optical absorption coefficient of 10 5 cm - 1 . [ABSTRACT FROM AUTHOR]