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N-Methyl-2-hydroxy-1-ethanaminium lead iodide exhibits a low melting temperature (Tm = 99 °C) among 2D hybrid metal halides (HMHs). This discovery expands the low melting characteristics of 2D HMHs to include a stepped 9R-like structure, suggesting significant potential for melt-processing and hybrid glass formation. [ABSTRACT FROM AUTHOR]

Precursor solution aging process can cause significant influence on the photovoltaic performance of perovskite solar cells (PVSCs). Notably, we first observe that the aging phenomenon is more severe in the precursor of two‐step sequential method compared to that in one‐step method due to that the protic solvent isopropanol facilitates amine‐cation side reaction and iodide ions oxidation. Herein, we report a novel approach for selectively stabilizing both organic amine salt and lead iodide (PbI2) precursor solutions in two‐step method. The introduction of benzene‐1,3‐dithiol into organic amine salt solution can mitigate amine‐cation side reactions due to the formation of an acidic and reducing environment. Simultaneously, decamethylferrocene (FcMe10/FcMe+10) pair can act as a redox shuttle in PbI2 solution to concurrently oxidize Pb0 and reduce I2 in cyclic manner. Consequently, the PVSCs device fabricated from ameliorative precursor solutions demonstrates superior power conversion efficiency of 25.31 %, retaining 95 % of its efficiency after 21 days of solution aging. Moreover, the unencapsulated devices maintain 85 % of primitive efficiency for 1500 h at maximum power point tracking under continuous illumination. This work establishes a fundamental guidance and scientific direction for the stabilization of two‐step perovskite precursor solutions. [ABSTRACT FROM AUTHOR]

The perovskite solar cells (PSCs) reveal the impressive performance due to the extraordinary characteristic features of perovskite material and its fabrication methods. The complex deposition process and hygroscopic nature of hole transport materials are biggest obstacles for attaining high power conversion efficiency (PCE) with long term stability in PSC. In this study, NiO/MWCNT nanocomposites have been synthesized by hydrothermal method and are incorporated in CH 3 NH 3 PbI 3 to increase the performance of PSCs with stability. The incorporation has been carried out to improve the properties of CH 3 NH 3 PbI 3 such as formation of large grain size/grain boundaries, reduce the defects that enhance the charge generation/collection and reduction in recombination. The fabricated PSCs with NiO/MWCNT revealed a PCE of 14.93 % with moderate hysteresis, which is significantly higher PCE than that of pristine PSC. The enhanced recombination resistance was observed by electrochemical impedance spectroscopy, which evinces the remarkable PCE of NiO/MWCNT incorporated PSC. The strong PL quenching and red shift of PL spectrum confirms the low recombination and larger grains in the NiO/MWCNT-CH 3 NH 3 PbI 3 layer. Moreover, the NiO/MWCNT incorporated PSC retains 94 % of its initial PCE after 600 h of aging under atmospheric condition whereas the PCE of pristine PSC shows 87 % of its initial PCE value. The carbon back electrode also supports to lift up PCE and stability of PSCs. [ABSTRACT FROM AUTHOR]

Rational design of chiral two‐dimensional hybrid organic–inorganic perovskites is crucial to achieve chiroptoelecronic, spintronic, and ferroelectric applications. Here, an efficient way to manipulate the chiroptoelectronic activity of 2D lead iodide perovskites is reported by forming mixed chiral (R‐ or S‐methylbenzylammonium (R‐MBA+ or S‐MBA+)) and achiral (n‐butylammonium (nBA+)) cations in the organic layer. The strongest and flipped circular dichroism signals are observed in (R/S‐MBA0.5nBA0.5)2PbI4 films compared to (R/S‐MBA)2PbI4. Moreover, the (R/S‐MBA0.5nBA0.5)2PbI4 films exhibit pseudo‐symmetric, unchanged circularly polarized photoluminescence peak as temperature increases. First‐principles calculations reveal that mixed chiral–achiral cations enhance the asymmetric hydrogen‐bonding interaction between the organic and inorganic layers, causing more structural distortion, thus, larger spin‐polarized band‐splitting than pure chiral cations. Temperature‐dependent powder X‐ray diffraction and pair distribution function structure studies show the compressed intralayer lattice with enlarged interlayer spacing and increased local ordering. Overall, this work demonstrates a new method to tune chiral and chiroptoelectronic properties and reveals their atomic scale structural origins. [ABSTRACT FROM AUTHOR]

Formamidinium lead iodide (FAPbI3) is the benchmark material for the most efficient near‐infrared perovskite light‐emitting diodes (LEDs) and a promising gain medium for perovskite‐based coherent light sources. Thus, it is crucial to understand and control its defect chemistry to harness the full potential of its exceptional radiative recombination properties. Here, this topic is addressed by tailoring the I− to Br− ratio in the perovskite composition. It is found that introducing small Br− quantities improves the yield of radiative recombination with a beneficial impact on both spontaneous and amplified spontaneous emission (ASE) and improves the semiconductor photostability leading to reduced luminescence efficiency roll‐off and enhanced radiance in LEDs. By employing photoemission electron microscopy (PEEM), this improvement in optoelectronic performance can be directly correlated to a reduced hole‐trapping activity achieved by replacing iodide with bromide, thus, providing a convenient yet powerful synthetic approach to control the defect chemistry of the material and fostering its implementation in advanced photonic platforms. [ABSTRACT FROM AUTHOR]

Single‐crystal hybrid perovskites represent an emerging class of next‐generation semiconductors due to their excellent and tunable optoelectronic properties, along with a solution‐based, low‐temperature growth process. 2D single‐crystal hybrid perovskites are especially promising as their long‐range ordered multiple quantum well structure induces many peculiar properties, such as large exciton binding energy, large in‐plane conductivity, and improved environmental stability, which make them suitable for low‐dimensional optoelectronics applications and fundamental studies. Herein, the structural properties, morphology, and optoelectronic behavior of 2D thin film phenethylammonium lead iodide (PEA2PbI4) single‐crystals, synthesized using the space‐confined growth technique are explored. A planar device is fabricated and its spectral photoresponse is studied under broadband supercontinuum white light. Remarkably, the device exhibits an ultra‐low dark current (10−14 A), indicative of low defect density and suppressed ion migration. Under white light, the current increases linearly with the incident power, up to a factor of 105, and the device achieves a specific detectivity of 109 Jones. The temperature and wavelength dependence of the photocurrent suggests the dissociation of excitons as one of the main mechanisms affecting photoconduction. Furthermore, stability under air exposure and illumination turns out to be remarkable. [ABSTRACT FROM AUTHOR]

Photocatalytic water splitting using semiconductors is a promising approach for converting solar energy to clean energy. However, challenges such as sluggish water oxidation kinetics and limited light absorption of photocatalyst cause low solar‐to‐hydrogen conversion efficiency (STH). Herein, we develop a photocatalytic overall water splitting system using I3−/I− as the shuttle redox couple to bridge the H2‐producing half‐reaction with the O2‐producing half‐reaction. The system uses the halide perovskite of benzylammonium lead iodide (PMA2PbI4, PMA=C6H5CH2NH2) loaded with MoS2 (PMA2PbI4/MoS2) as the H2 evolution photocatalyst, and the RuOx‐loaded WO3 (WO3/RuOx) as the O2 evolution photocatalyst, achieving a H2/O2 production in stoichiometric ratio with an excellent STH of 2.07 %. This work provides a detour route for photocatalytic water splitting with the help of I3−/I− shuttle redox couple in the halide perovskite HI splitting system and enlightens one to integrate and utilize multi catalytic strategies for solar‐driven water splitting. [ABSTRACT FROM AUTHOR]

Conjugated organic cations are intriguing for organic‐inorganic halide perovskites due to their direct participation in the optoelectronic properties of hybrid materials. In conjugated cations, the dihedral angle, or torsion angle, between adjacent aromatic rings is a critical secondary structural element. This angle influences not only the shape of the cations but also the overlap between the π‐orbitals on adjacent rings, thereby affecting their electronic properties. Understanding how variations in the dihedral angle impact the structure and properties of hybrid organic‐inorganic metal halides (HOIMHs) is fundamentally important. In this study, we utilized 2,2′‐dimethyl bipyridinium as the organic cation, reacting it with PbI₂ to form hybrid lead iodides. Remarkably, variations in the dihedral angle between the two pyridinium rings resulted in the formation of two distinct crystal structures with different band gaps. Our findings demonstrate that manipulating the dihedral angle offers a novel approach to controlling the structures and properties of hybrid metal halides with conjugated cations. [ABSTRACT FROM AUTHOR]

Mixed tin‐lead perovskite solar cells can reach band gaps as low as 1.2 eV, offering high theoretical efficiency and serving as base materials for all‐perovskite tandem solar cells. However, instability and high defect densities at the interfaces, particularly the buried surface, have limited performance improvements. In this work, we present the modification of the bottom perovskite interface with multifunctional hydroxylamine salts. These salts can effectively coordinate the different perovskite components, having critical influences in regulating the crystallization process and passivating defects of varying nature. The surface modification reduced traps at the interface and prevented the formation of excessive lead iodide, enhancing the quality of the films. The modified devices presented fill factors reaching 81 % and efficiencies of up to 23.8 %. The unencapsulated modified devices maintained over 95 % of their initial efficiency after 2000 h of shelf storage. [ABSTRACT FROM AUTHOR]

The two‐step sequential deposition method is considered a potential way for the large‐scale manufacture of perovskite solar cells (PSCs) with high power conversion efficiency and reproducibility. However, the dense lead iodide (PbI2) film interferes with its full contact with organic solutions, resulting in an inadequate reaction at the interface. Herein, 2 kinds of metal‐organic framework (MOF) are introduced, amorphous Ni‐MOF‐74 (amNi‐MOF‐74) and crystalline Zn‐MOF‐74 (crZn‐MOF‐74), into PbI2 for regulating crystallization. Compared to crZn‐MOF‐74, the incorporation of amNi‐MOF‐74 exhibited rapid nucleation, resulting in high‐quality perovskite films with large grain size, low trap density, and enhanced charge transfer between the perovskite and charge transfer layers. Meanwhile, the content of unstable phase PbI2 left in perovskite films due to insufficient reaction is also reduced. The amNi‐MOF‐74 modified PSCs exhibited a champion power conversion efficiency of 24.17% with good humidity and thermal stability. The unencapsulated device maintains 90% of its initial efficiency after 1000 h storage in dark ambient conditions with ≈30% relative humidity. This strategy provides an effective approach for promoting the crystallization process of perovskite and fabricating efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid perovskite solar cells (HPSCs) are gaining attention as a promising technology for next‐generation photovoltaic devices owing to their impressive power conversion efficiency (PCE) and cost‐effective fabrication methods. Although, solution‐processed passivation using 2D perovskites can improve the interface recombination, this approach hampers its effective charge transportation. In this study, the study investigates the properties and performance of the bilayer 3D/3D methylammonium lead iodide (MAPbI3)/formamidinium lead iodide (FAPbI3)‐based perovskite heterojunction (BPHJ) to address these concerns. The bilayer structure consists of two distinct perovskite absorbers having independent structure that are sandwiched between two charge transporting layer (CTLs) to make functional device. First, the fabrication process is optimized to achieve high‐quality MAPbI3 perovskite films with controlled morphology and crystallinity followed by the formation of BPHJ using FAPbI3 deposition by thermal evaporation technique. The BPHJ‐160 nm‐based PSCs with optimized parameters exhibit an enhanced PCE of 23.08% compared to single‐layer reference (20.15%) device. The improved performance can be attributed to the effective charge extraction at the heterojunction interface and reduced charge recombination losses due to favorable energy levels. Furthermore, the long‐term stability of the BPHJ‐based perovskite device is assessed under continuous illumination along with its ambient and thermal stability across different environmental conditions. [ABSTRACT FROM AUTHOR]

Metal–halide perovskites have gained extreme interest in the photovoltaic field with formamidinium lead iodide (FAPbI3) currently being one of the best‐performing materials for single‐junction solar cells. Despite the outstanding record efficiencies, there are still several major issues hindering the large‐scale fabrication of perovskite solar cells. The vulnerability to environmental agents along with the need of controlled atmosphere and crystallization aids for the perovskite film deposition represents the major roadblocks. This is particularly true for FAPbI3 for which the thermodynamically stable phase at room temperature is photovoltaically inactive δ‐phase. To address those challenges, herein, a camphorsulfonic‐salified chitosan is specifically designed with the aid of DTF calculations to strongly interact with the perovskite and, as a result, improve the morphology and optoelectronic quality of the FAPbI3. Thanks to the numerous interactions and then the modulation of the solution viscosity, FAPbI3 devices are fabricated by gravure printing deposition without either antisolvent bath or inclusion of methylammonium chloride (MACl) as additive. The gravure‐printed devices with the chitosan feature an enhanced efficiency and stability in air, retaining 80% of the original efficiency after 1200 h in ambient air without any encapsulation. [ABSTRACT FROM AUTHOR]

Dimensional engineering is promising for achieving a high power conversion efficiency (PCE) and long‐term stability of perovskite solar cells (PSCs). However, insulated organic spacers in 2D perovskites often severely hinder carrier transport between the internal layers of devices. Herein, the “protonation‐induced localized transformation of 2D perovskites” is proposed to overcome the low carrier transport and conductivity of 2D/3D perovskite heterojunctions. Metformin, with its multiple amine groups and a substantial difference between its pKa value and perovskites, is protonated in an acidic environment or directly converted into the hydrochloride salt for the surface passivation of methylammonium lead iodide. This leads to the transformation of disorderedly oriented layered 2D perovskite into vertically oriented ones at grain boundaries. Consequently, the PCE of a carbon‐based PSC treated by protonated metformin increased considerably, reaching an optimal level of 14.13%. Additionally, applying this passivation strategy to a planar device (ITO/4PADCP/perovskite/PCBM/BCP/Ag) increased PCE from 20.82% to 22.09%, confirming the applicability of the strategy. To demonstrate the practical stability, an integrated PSC–supercapacitor device is assembled, which shows good cycling stability. This article introduces a novel method to improve carrier transport in 2D/3D perovskite heterojunctions, promoting the extensive utilization of dimensional engineering. [ABSTRACT FROM AUTHOR]

As a van der Waals (vdW) layered semiconductor material, lead iodide (PbI2) possessing a direct bandgap with strong photoluminescence emission in visible range has gained wide attention in applications of photonic and optoelectronic devices. Here, upconversion photoluminescence (UPL) in exfoliated PbI2 flakes is demonstrated at room temperature and elevated temperatures. The linear power dependence of UPL emission with 532 nm excitation suggests the one-photon involved multiphonon-assisted UPL emission process, which is revealed by the temperature-dependent UPL emission measurement. Meanwhile, the nonlinear power dependence of UPL emission with 561 nm excitation indicates the transition of UPL emission mechanism from linear to nonlinear regime, and the temperature-dependent UPL emission study further shows that the upconversion is contributed by both the multiphonon-assisted UPL process and the two-photon absorption induced PL process. This study will provide an insight to the understanding of photon upconversion in vdW layered semiconductors and advancing applications in temperature-controlled photon upconversion, tunable photonics, photodetection and imaging. [ABSTRACT FROM AUTHOR]

Surface treatment of perovskite materials with their layered counterparts has become an ubiquitous strategy for maximizing device performance. While layered materials confer great benefits to the longevity and long‐term efficiency of the resulting device stack via passivation of defects and surface traps, numerous reports have previously demonstrated that these materials evolve under exposure to light and humidity, suggesting that they are not fully stable. Therefore, it is crucial to study the behavior of these materials in isolation and in conditions mimicking a device stack. Here, it is shown that perovskite capping layers templated by a range of cations on top of methylammonium lead iodide devolve in conditions commonly found during perovskite fabrication, such as exposure to light, solvent, and moisture. Photophysical, structural, and morphological studies are used to show that the degradation of these layered perovskites occurs via a self‐limiting, pinhole‐mediated mechanism. This results in the loss of whole perovskite sheets, from a few monolayers to tens of nanometers of material, until the system stabilizes again as demonstrated for exfoliated flakes of PEA2PbI4. This means that initially targeted structures may have devolved, with clear optimization implications for device fabrication. [ABSTRACT FROM AUTHOR]

Chiral hybrid organic–inorganic perovskites (HOIPs) have garnered considerable research interest in the field of optoelectronics, owing to their ability to integrate outstanding optoelectronic characteristics with distinct chiral or spin‐related properties. Although recent years have witnessed the rapid development of chiral perovskites, methods for producing perovskites with high absorption dissymmetry factors (gCD) enabling polarization‐resolved chiroptical applications are still lacking. This study introduces a strategic combination of dual spacer cations, i.e., achiral hexane‐1,6‐diammonium (HDA) and chiral 1‐(chlorophenyl)ethylammonium (ClPEA), for boosting the chiroptical performance of 2D lead iodide HOIPs. Interestingly, ortho‐ClPEA, incapable of forming 2D HOIPs independently, successfully creates 2D structures in collaboration with HDA, exhibiting CD signals aligned with the absorption characteristics of 2D HOIPs. This significant milestone leads to an outstanding gCD value of 0.018, positioning it among the top performers in the field of lead‐based HOIPs. Furthermore, this study demonstrates the fabrication of circularly polarized light (CPL) detectors with a photocurrent dissymmetry factor (gIph) of 0.12, utilizing the HOIPs with enhanced chiroptical activity. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are performed to study the crystallization of formamidinium lead iodide. From all-atom simulations of the crystal growth process and the δ-α-phase transitions, we try to reveal the formation of various stack-faulted intermediate defected structures and report various polytypes of formamidinium lead iodide that are observed from simulations. [ABSTRACT FROM AUTHOR]

This study aims to contribute to the development of theoretical and experimental tools for characterizing the transport properties of perovskite semiconductors. In the context of existing transport characterization methods for perovskites, there is a need for techniques that can accurately assess the critical transport parameters, such as diffusion lengths, given the specific challenges posed, such as their inherent instabilities. The novel methodology employed involves the development of a theoretical model to describe the running fringes-induced photo-electromotive force (RF photo-EMF) effect in bipolar photoconductors with a rather general type of photoconductivity relaxation behaviors for both carriers. This model is founded on the theory of photoinduced space charge grating formation in semiconductors. Subsequently, RF photo-EMF experiments were conducted on methylammonium lead iodide (CH 3 NH 3 PbI 3 or MAPI) polycrystalline films of varying grain sizes. By utilizing the RF photo-EMF technique, we successfully elucidated crucial transport and recombination characteristics, notably the ambipolar diffusion length and relaxation times of the charge carriers. Significantly, the developed theoretical model exhibited a remarkable agreement with the experimental results, highlighting its ability in explaining and predicting the behavior of charge carriers in perovskite semiconductors. The results of this study make a substantial contribution to the field of perovskite semiconductors by offering a novel theoretical and experimental approach to characterization of perovskites' transport properties. [ABSTRACT FROM AUTHOR]

Using muon spin relaxation measurements on formamidinium lead iodide [ FAPbI 3 , where FA denotes HC( NH 2) 2 ], we show that, among the five structurally distinct phases of FAPbI 3 exhibited through two different temperature hysteresis, the reorientation motion of FA molecules is quasi-static below ≈ 50 K over the time scale of 10 − 6 s in the low-temperature (LT) hexagonal (Hex-LT, <160 K) phase, which has a relatively longer photo-excited charge carrier lifetime (τ c ∼ 10 − 6 s). In contrast, a sharp increase in the FA molecular motion was found above ≈ 50 K in the Hex-LT phase, LT-tetragonal phase (Tet-LT, <140 K), the high-temperature (HT) hexagonal phase (Hex-HT, 160–380 K), and the HT-tetragonal phase (Tet-HT, 140–280 K), where τ c decreases with increasing temperature. More interestingly, the reorientation motion is further promoted in the cubic phase at higher temperatures (>380/280 K), while τ c is recovered to comparable or larger than that of the LT phases. These results indicate that there are two factors that determine τ c , one related to the local reorientation of cationic molecules that is not unencumbered by phonons and the other to the high symmetry of the bulk crystal structure. [ABSTRACT FROM AUTHOR]

Using muon spin relaxation measurements on formamidinium lead iodide [ FAPbI 3 , where FA denotes HC( NH 2) 2 ], we show that, among the five structurally distinct phases of FAPbI 3 exhibited through two different temperature hysteresis, the reorientation motion of FA molecules is quasi-static below ≈ 50 K over the time scale of 10 − 6 s in the low-temperature (LT) hexagonal (Hex-LT, <160 K) phase, which has a relatively longer photo-excited charge carrier lifetime (τ c ∼ 10 − 6 s). In contrast, a sharp increase in the FA molecular motion was found above ≈ 50 K in the Hex-LT phase, LT-tetragonal phase (Tet-LT, <140 K), the high-temperature (HT) hexagonal phase (Hex-HT, 160–380 K), and the HT-tetragonal phase (Tet-HT, 140–280 K), where τ c decreases with increasing temperature. More interestingly, the reorientation motion is further promoted in the cubic phase at higher temperatures (>380/280 K), while τ c is recovered to comparable or larger than that of the LT phases. These results indicate that there are two factors that determine τ c , one related to the local reorientation of cationic molecules that is not unencumbered by phonons and the other to the high symmetry of the bulk crystal structure. [ABSTRACT FROM AUTHOR]

Organic‐inorganic hybrid perovskite materials, such as formamidinium lead iodide (FAPbI3), are among the most promising emerging photovoltaic materials. However, the spontaneous phase transition from the photoactive perovskite phase to an inactive non‐perovskite phase complicates the application of FAPbI3 in solar cells. To remedy this, alkali metal cations, most often Cs+, Rb+ or K+, are included during perovskite synthesis to stabilize the photoactive phase. The atomic‐level mechanisms of stabilization are complex. While Cs+ dopes directly into the perovskite lattice, Rb+ does not, but instead forms an additional non‐perovskite phase, and the mechanism by which Rb confers increased stability remains unclear. Here, we use 1H−87Rb double resonance NMR experiments to show that FA+ incorporates into the Rb‐based non‐perovskite phases (FAyRb1‐yPb2Br5 and δ‐FAyRb1‐yPbI3) for both bromide and iodide perovskite formulations. This is demonstrated by changes in the 1H and 87Rb chemical shifts, 1H−87Rb heteronuclear correlation spectra, and 87Rb{1H} REDOR spectra. Simulation of the REDOR dephasing curves suggests up to ~60 % FA+ incorporation into the inorganic Rb‐based phase for the bromide system. In light of these results, we hypothesize that the substitution of FA+ into the non‐perovskite phase may contribute to the greater stability conferred by Rb salts in the synthesis of FA‐based perovskites. [ABSTRACT FROM AUTHOR]

Continuous heat generation in perovskite solar cells (PSCs), caused by solar radiation, poses a significant challenge to their lifespan. Existing active cooling methods require extra energy input and might not be effective at high temperatures. Most reported passive radiative cooling materials either lack solar transparency or require complex fabrication processes. Here, mesoporous silica nanoparticles are designed, synthesized, and assembled into multilayered stacks with a graded refractive index (GRI) by spray coating them on top of PSCs made from methylammonium lead iodide (MAPbI3) over a large scale (15.6 × 15.6 cm2). This coating offers both high transparency in the visible wavelength and high emissivity in the mid‐infrared region, leading to an average temperature reduction of 6.65 ±  1.48 °C in GRI‐coated MAPbI3 PSCs under outdoor conditions compared to non‐coated references. After 50 d, the GRI‐coated PSCs maintain 80.9 ± 8.7% of their initial photoconversion efficiency, in contrast to 6.1 ± 5.9% for the noncoated ones. The calculated cooling power of the GRI‐coated PSCs is 28.9% higher than that of the reference cells. [ABSTRACT FROM AUTHOR]

The highly oriented 2D perovskite templates of n = 1 have typically been created to attain controllable and oriented crystallization of 3D α‐phase formamidinium lead triiodide (α‐FAPbI3) perovskites. However, the role of methylammonium iodide (MAI), a widely used α‐FAPbI3 phase stabilizer, in regulating the growth dynamics of 2D/3D perovskites is generally ignored. Herein, Ruddlesden–Popper type n = 1 2D octylammonium lead iodide (OA2PbI4) perovskites are added into FAPbI3 precursor solution. The template of n = 2 (OA2MAPb2I7), which is spontaneously constructed by the mixture of n = 1 2D and methylammonium chloride (MACl), acts as a skeleton to template the epitaxial growth of α‐FAPbI3. However, the volatilization of MACl inevitably causes damage to the 2D structure during thermal annealing. This study reveals that small amounts of less volatile MAI additive enables the creation of stable 2D template, leading to more controlled vertical orientation crystallization. Consequently, the high‐quality mixed‐dimensional perovskite film delivers a high efficiency of 24.19% together with improved intrinsic stability. This work provides an in‐depth understanding of 2D‐assisted controlled epitaxial growth of α‐FAPbI3. [ABSTRACT FROM AUTHOR]

Reconfigurable phototransistors featuring bipolar photoresponses are favorable for manipulating high-performance neuromorphic vision sensory. Here, we present a momentum-conserved reconfigurable phototransistor based on the van der Waals heterojunction between methylammonium lead iodide perovskite and two-dimensional Bi2O2Se semiconductor, which exhibits a synergistic interplay of interband hot-carrier transitions and reconfigurable heterointerface band alignments, eventually achieving the ultrahigh bipolar optoelectronic performances with the photoresponsivity of 6×107 AW−1, accompanied by the specific detectivity of 5.2×1011 Jones, and the dynamic range of 110 dB. Moreover, A 3×3 heterotransistor array is fabricated to perform in-sensor analog multiply-accumulate operations even under the challenging dim illumination of 0.1 μWcm−2 that comparable to natural moonlight. The reconfigurable heterotransistor array can be further adopted to enhance the traffic-light detection under dim-light conditions. Our advancement in momentum-conserved reconfigurable heterotransistor signifies a leap forward in real-time, energy-efficient, and low-light image processing for neuromorphic vision sensors. Xu et al. report reconfigurable phototransistors based on MAPbI3/Bi2O2Se heterostructure, with momentum conservation promotes hot carrier extraction and interlayer carrier transport. Heterotransistor array enables traffic light signal detection under dim light, assisted by YOLOv4 neural network. [ABSTRACT FROM AUTHOR]

The lead iodide (PbI2) in lead‐halide perovskite (LHP) is both a positive additive for material properties and a site for the formation of device defects. Therefore, atomic‐level detection of PbI2 and its derived Pb structures are crucial for understanding the performance and stability of the LHP material. In this work, the atomic imaging of the LHP, PbI2, and Pb lattices is achieved using low‐dose integrated differential phase contrast (iDPC) scanning transmission electron microscopy (STEM). Combining it with the traditional high‐angle annular dark field (HAADF)‐STEM, the Pb precipitation in different LHPs (CsPbI3, CsPbBr3, and FAPbI3) and under different conditions (light, air, and heat) can be investigated in real space. Then, the features of Pb precipitation (positions and sizes) are visually revealed under different conditions and the stabilities of different LHPs. Meanwhile, the pathway of Pb precipitation is directly imaged and confirmed by the iDPC‐STEM during an in situ heating process, supporting the detailed mechanism of Pb precipitation. These results provide the visual evidence for analyzing atomic Pb precipitation in LHPs, which helps better understand the structure‐property relation induced by Pb impurity. [ABSTRACT FROM AUTHOR]

Hybrid organometal halide perovskites (HP) present exceptional optoelectronic properties, but their poor long‐term stability is a major bottleneck for their commercialization. Herein, a solvent‐free approach to growing single‐crystal organic nanowires (ONW) is presented, along with nanoporous metal oxide scaffolds and HP, to form a core@multishell architecture. The synthesis is carried out under mild vacuum conditions employing thermal evaporation for the metal‐free phthalocyanine (H2Pc) nanowires, which are the core, plasma‐enhanced chemical vapor deposition (PECVD) for the TiO2 shell, and co‐evaporation of lead iodide (PbI2) and methylammonium iodide (CH3NH3I/MAI) for the CH3NH3PbI3 (MAPbI3/MAPI) perovskite shell. A detailed characterization of the nanostructures by electron microscopy, (S)‐TEM, and X‐ray diffraction, XRD, is presented, revealing a different crystallization of the HP depending on the template: while the growth on H2Pc nanowires induces the typical MAPI tetragonal structure, a low‐dimensional phase (LDP) is observed on the 1D‐TiO2 nanotubes. Such a combination yields an unprecedentedly stable photoluminescence emission over 20 h and over 300 h after encapsulation in polymethyl methacrylate (PMMA) under different atmospheres including N2, air, and high moisture levels. Moreover, the unique 1D morphology of the system, together with the high refractive index, allows for a strong waveguiding effect along the HP nanowire length. [ABSTRACT FROM AUTHOR]

Low‐dimensional metal halide perovskites exhibit exceptional photoelectronic properties and intrinsic stability, positioning them as a promising class of semiconductor materials for light‐emitting devices and photodetectors. In this work, we present a millimeter‐scale single crystal of mixed low‐dimensional (one‐dimensional–zero‐dimensional [1D–0D]) organic lead iodide with well‐defined crystallinity. The fabricated single‐crystal devices demonstrate high‐sensitivity photoresponse and x‐ray detection performance. By spatially isolating organic molecules to form the mixed 1D–0D crystal structure, ion migrations is effectively suppressed, resulting in a remarkable three orders of magnitude reduction in the dark current (56.4 pA @200 V) of the single‐crystal devices. Furthermore, by enhancing the background characteristics, we achieved an impressive low x‐ray detection limit of 154.5 nGys−1 in the single‐crystal device. These findings highlight that the mixed 1D–0D organic lead iodide configuration efficiently controls ion migration within the crystal structure, offering a promising avenue for realizing high‐performance perovskite‐based photodetectors and x‐ray detectors. [ABSTRACT FROM AUTHOR]

The stabilization of the formamidinium lead iodide (FAPbI 3) structure is pivotal for the development of efficient photovoltaic devices. Employing two-dimensional (2D) layers to passivate the three-dimensional (3D) perovskite is essential for maintaining the α-phase of FAPbI 3 and enhancing the power conversion efficiency (PCE) of perovskite solar cells (PSCs). However, the role of bulky ligands in the phase management of 2D perovskites, crucial for the stabilization of FAPbI 3 , has not yet been elucidated. In this study, we synthesized nanoscale 2D perovskite capping crusts with < n > = 1 and 2 Ruddlesden-Popper (RP) perovskite layers, respectively, which form a type-II 2D/3D heterostructure. This heterostructure stabilizes the α-phase of FAPbI 3 , and facilitates ultrafast carrier extraction from the 3D perovskite network to transport contact layer. We introduced tri-fluorinated ligands to mitigate defects caused by the halide vacancies and uncoordinated Pb2+ ions, thereby reducing nonradiative carrier recombination and extending carrier lifetime. The films produced were incorporated into PSCs that not only achieved a PCE of 25.39% but also maintained 95% of their initial efficiency after 2000 h of continuous light exposure without encapsulation. These findings underscore the effectiveness of a phase-pure 2D/3D heterostructure-terminated film in inhibiting phase transitions passivating the iodide anion vacancy defects, facilitating the charge carrier extraction, and boosting the performance of optoelectronic devices. [ABSTRACT FROM AUTHOR]

This study compared the photoluminescence (PL) stabilities of formamidinium (FA) and methylammonium (MA) in lead iodide perovskite quantum dots (QDs). To exclude other factors, such as size and purity, that may affect stability, MAPbI3 and FAPbI3 QDs with nearly identical sizes (~10.0 nm) were synthesized by controlling the ligand concentration and synthesis temperature. Transmission electron microscopy images and X‐ray diffraction patterns confirmed homogeneous single‐phase perovskite structures. Additionally, the bandgaps and sizes of the synthesized QDs closely matched those of the infinite quantum well model, which guaranteed that the photostability was solely caused by the different organic molecules in the two QDs. We analyzed the PL peak centers and full‐width at half maximum of the QDs for 32 days. The enhanced stability of FAPbI3 was found to be caused by the nearly zero redshift (1.615 eV) of its PL peak, in contrast to the redshift (1.685→1.670 eV) of MAPbI3. [ABSTRACT FROM AUTHOR]

We present the formation of a composite film made out of formamidinium lead iodide (FAPI) and molybdenum disulphide quantum dots (MoS2 QDs) and propose a corresponding photovoltaic device architecture based on a 'type-I' alignment of the two materials' electronic energy levels. The introduction of the MoS2 QDs has not compromised the overall crystallinity of the FAPI film and the composite absorber has shown improved stability. We report on the benefits of this composite film and energy band arrangement as the photogenerated carriers in MoS2 QDs, both positive and negative, are injected into the FAPI host matrix, resulting in an increased current density of 24.19 mA cm−2 compared to a current density of 19.83 mA cm−2 for the control device with FAPI only. The corresponding photoconversion efficiency increases from 12.6 to 15.0%. We also show that inclusion of MoS2 QDs in FAPI films resulted in a notable improvement in the fill factor and open-circuit voltage of the solar cells. Most importantly, MoS2 QDs enhanced the film stability by reducing defect formation and acting as passivating agents that minimize recombination losses and improve charge carrier transport. Our results suggest that a composite film in a type-I device architecture can introduce benefits for both future developments in perovskite solar cells and effectively tackling the longstanding challenges of carrier transport in QDs solar cells. [ABSTRACT FROM AUTHOR]

High‐quality perovskite (PVK) films is essential for the fabrication of efficient and stable perovskite solar cells (PSCs). However, unstable colloidal particles in PVK suspensions often hinder the formation of crystalline films with low defect densities. Herein, ethylenediaminetetraacetic acid (EDTA) as a colloidal stabilizer into lead iodide (PbI2) is introduced colloidal solutions. EDTA forms chelated complexes with Pb2+, enhancing the electrostatic repulsion and steric hindrance between colloidal particles. This stabilizes the particles and inhibits disordered motion (Brownian motion) and excessive aggregation. As a result, PbI2 films with a uniform hole distribution are formed, providing ample pathways for subsequent PVK film growth and sufficient space. During the film formation process, the replacement of molecules by formamidinium iodide (FAI) and EDTA slows down crystallization, ultimately leading to PVK films with large grain sizes and low defect density. By using this approach, champion power conversion efficiencies (PCEs) of 24.05% for FA0.97Cs0.03PbI3 PSC, 11.08% for CsPbBr3 PSC, and 25.19% for FA0.945MA0.025Cs0.03Pb(I0.975Br0.025)3 PSC are achieved. Moreover, the EDTA‐based FA0.97Cs0.03PbI3 device retains over 90% of its initial PCE after 1000 h at the maximum power point (MPP) under continuous illumination. [ABSTRACT FROM AUTHOR]

Layered (2D) perovskites are an emerging attractive 2D system with enhanced stability to ambient conditions as opposed to their highly unstable three dimensional bulk counterpart. Their uniquely tuneable optical and electrical properties are underpinning a surge of interest in 2D‐photovoltaics. So far, the development of nano‐scale integrated opto‐electronic 2D perovskite devices remains nearly unexplored since they have generally been found to be incompatible with standard top‐down semiconductor nano‐fabrication technologies. Here, following the synthesis of solvent‐stable 2D‐fluorinated phenethylammonium lead iodide perovskite (F‐PEA)2PbI4 (F‐PEAI), planar photodetectors entirely fabricated in atmosphere is demonstrated, exhibiting figures of merit rivalling those of commercial silicon photodiodes. A record large room temperature detectivity (>5 × 1017 Jones), a fast time photoresponse (rise time 1.5 ns), an extraordinarily large linear dynamic range (228 dB), as well as a photo‐responsivity of ≈ 1100 AW−1 are demonstrated for devices on a range of substrates including flexible wearable media without the need for any planarization or any atomically thin dielectric, in stark contrast to other 2D semiconductors. Finally, the suitability of nano‐scale 2D F‐PEAI photodetector arrays with sub‐wavelength pixel size of just 100 nm of use for high definition imaging is demonstrated. [ABSTRACT FROM AUTHOR]

Inorganic CsPbI3 perovskite has exhibited great application potential in perovskite solar cells (PSCs) due to its suitable optical bandgap and high chemical stability. However, the perovskite phases of CsPbI3 are not stable at room temperature, where they transition to non-perovskite phases. Humidity or water has been thought to be the primary factor inducing this phase transition, which should be avoided throughout the procedure of film and device processing. Surprisingly, the present study indicates that preparing a precursor solution in humid air is beneficial to the growth of high-quality CsPbI3 perovskite to enhance device performance. It is demonstrated that the incorporation of H2 O in the precursor solution from humid air or by intentional addition significantly changes the composition of coordination compounds and increases the amount of low iodine coordination complexes. As a result, the crystallization of dimethylammonium lead iodide (DMAPbI3) intermediate is suppressed well, which accelerates its subsequent conversion to CsPbI3 perovskite. Consequently, an oriented CsPbI3 perovskite film with improved crystallinity and lower defect density is obtained. Most importantly, carbon-based PSCs (C-PSCs) based on the CsPbI3 perovskite film achieve an efficiency of 16.05%, a new record for inorganic C-PSCs. [ABSTRACT FROM AUTHOR]

Herein, a new energy cycle called the "hydrogen iodide (HI) cycle" is proposed that involves the repeated generation of solar hydrogen and battery power. Solar hydrogen generation using an HI solution allows for the use of a narrow‐bandgap photocatalyst. It is demonstrated that the addition of single‐walled carbon nanotubes (SWCNTs) effectively enhances solar hydrogen generation from HI solution with methylammonium lead iodide. Electron microscopy observations and spectroscopic experiments reveal that SWCNTs improve hydrogen generation by adsorbing byproduct iodine molecules. Additionally, a zinc‐iodine battery, utilizing paper I@SWCNTs recovered from the photocatalyst test cell and zinc metal, operates efficiently with an initial cell voltage of approximately 1.2 V. The battery's capacity, corresponding to the amount of encapsulated iodine molecules, indicates that SWCNTs can effectively adsorb the byproduct iodine molecules within the photocatalyst test cell. It is also discussed that the electrolyte solution after the discharge experiment should include iodide ions, indicating that the solution after battery discharge returns to the starting point of the "HI cycle." Raman measurements reveal that I@SWCNTs are transformed back into empty tubes during the discharge experiment. Therefore, SWCNTs can be repeatedly used in the new cyclic energy scheme referred to as the "HI cycle." [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrid perovskites like methylammonium lead iodide (MAPbI3) have received extensive attention in solar energy conversion due to their superb optoelectronic properties. However, the serious charge recombination at the nanoscale domain and the lack of catalytic sites on the perovskite's surface seriously limit their photocatalytic hydrogen evolution activities. Taking MAPbI3 as a typical example, we show that coupling amorphous molybdenum phosphide (MoP) cocatalyst with MAPbI3 can significantly enhance the photocatalytic H2 evolution performance of MAPbI3. The MoP coupling can accelerate the electron extraction from MAPbI3 and promote the hydrogen evolution reaction catalysis. Consequently, the photocatalytic hydrogen evolution activity of MoP/MAPbI3 is ca. 97 times higher than that of bare MAPbI3. Moreover, the MoP/MAPbI3 exhibits good stability during cycling tests. This work demonstrates the possibility of employing amorphous MoP as a non-noble metal-based cocatalyst in a hybrid perovskite-based photocatalytic hydrogen production reaction. Methylammonium lead iodide (MAPbI3) loaded with molybdenum phosphide (MoP) cocatalyst demonstrates 97 times higher photocatalytic hydrogen evolution activity than bare MAPbI3 from HI splitting reaction under visible light irradiation. [ABSTRACT FROM AUTHOR]

The efficiency and reproducibility of perovskite solar cells (PSCs) are significantly influenced by the purity of lead iodide (PbI2) in the raw materials used. Pb(OH)I has been identified as the primary impurity generated from PbI2 in water-based synthesis. Consequently, a comprehensive investigation into the impact of Pb(OH)I impurities on film and device performance is essential. In this study, PbI2, with varying stoichiometries, was synthesized to examine the effects of different Pb(OH)I levels on perovskite device performance. The characterization results revealed that even trace amounts of Pb(OH)I impede the formation of precursor prenucleation clusters. These impurities also increase the energy barrier of the α-phase and facilitate the transition of the intermediate phase to the δ-phase. These effects result in poor perovskite film morphology and sub-optimal photovoltaic device performance. To address these issues, a cost-effective method for preparing high-stoichiometry PbI2 was developed. The formation of Pb(OH)I was effectively inhibited through several strategies: adjusting solution pH and temperature, modifying material addition order, simplifying the precipitation–recrystallization process, and introducing H3PO2 as an additive. These modifications enabled the one-step synthesis of high-purity PbI2. PSCs prepared using this newly synthesized high-stoichiometry PbI2 demonstrated photovoltaic performance comparable to those fabricated with commercial PbI2 (purity ≥ 99.999%). Our novel method offers a cost-effective alternative for synthesizing high-stoichiometry PbI2, thereby providing a viable option for the production of high-performance PSCs. [ABSTRACT FROM AUTHOR]

Developing efficient photoactive and environmentally stable methylammonium lead iodide (CH3NH3PbI3, MAPI) perovskite films in open-air conditions is challenging. This can be achieved by incorporating inorganic nanostructures into the MAPI perovskites. Recently, various shapes of inorganic nanostructures like PbS, CdS, and SnS have been included, but the effect of nanocuboids shapes has not been explored. In the present study, we studied the impact of adding PbS nanocuboids to MAPI perovskite. We found that incorporating these chemically grown PbS nanocuboids significantly improves MAPI perovskite material's optoelectronic properties. The PbS nanocuboids were synthesized using different concentrations of CTAB complexing agent. Then, using slot die coating, thin films of MAPI:PbS nanocomposite were prepared with different-sized PbS nanocuboids. With the incorporation of PbS nanocuboids, significant improvements have been observed in the optoelectronic properties of MAPI perovskite films. Finally, we fabricated pristine MAPI and MAPI:PbS nanocomposite-based photodetectors using a slot die coating on a TiO2-coated FTO substrate. Compared to pristine perovskite, the photodetector fabricated with the incorporation of 20% of PbS in MAPI (MAPI:PC-2) has the shortest decay time of 0.08 s and four-fold improvements in photosensitivity and the highest photodetectivity of 108.11 × 108 Jones with an external quantum efficiency of ~ 13.77%. We believe the enhanced optical absorption and efficient charge collection between the perovskite and hole transport layer may be responsible for the improved photodetector performance. These results suggest that incorporating PbS in MAPI perovskite holds promise for various optoelectronic applications. [ABSTRACT FROM AUTHOR]

Detailed investigation has been performed for the effect of in-situ substrate heating on the growth of printed perovskite films towards getting high performance perovskite solar cells (PSCs). Perovskite layers and charge transport layers were printed by slot die method. The perovskite layers were printed in two steps, where first lead iodide (PbI2) films were printed and then methyl ammonium iodide (MAI) ink was printed on them to convert PbI2 into methyl ammonium lead iodide (MAPbI3) perovskite. For the controlled growth of PbI2 crystals the printed PbI2 films were in-situ heated at different temperatures like 50oC, 70oC and 90oC that resulted in formation of compact films with different crystal growths and phases, which affected the growth of perovskite crystals thereafter. It was difficult to convert the compact PbI2 films completely into MAPbI3 by one time printing of MAI, therefore the idea of multiple print cycles of MAI was implemented. The optimized print cycles of MAI led to achieve complete conversion of PbI2 into high quality MAPbI3 crystals, which resulted in PSCs having champion power conversion efficiency (PCE) up to 11.99%. The steady state PCE of the optimized cell did not exhibit any decay for > 200 s. Under continuous 1 sun illumination of a tungsten-halogen lamp, the optimized cells retained over 50% of their initial efficiency for up to ∼ 300 h. Subsequently, the solar modules printed with optimum print conditions in 9 cm × 13 cm area with an active area of 64.8 cm2, exhibited PCE of 7.77%. [ABSTRACT FROM AUTHOR]

Lead iodide (PbI2) is a 2D layered semiconductor used in several electronic applications, such as solar cells, X-ray, and gamma-ray detectors. Most of its properties have been reported for monocrystals or polycrystalline thick films used in high-energy photon detectors. As for thin films used in other optoelectronic devices, the reported properties are limited to the conditions adopted in manufacturing the devices. Furthermore, very little is known about the properties of films deposited by sputtering. Here, we investigate the optical and structural properties of PbI2 thin films deposited by rf-sputtering a PbI2 target. The deposition temperature significantly influences the film's properties, as determined by X-ray, scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-vis, and Raman spectroscopy. A common characteristic at all temperatures was forming metallic lead (Pb) segregated in the surface of films, with concentration depending on the deposition temperature. These lead clusters were successfully converted into PbI2 using an iodination process, allowing the synthesis of pure PbI2 films without lead segregation. The activation energy for the reaction between Pb clusters and iodine vapor was determined by adopting the Arrhenius equation. It was also observed that converting PbI2 film into perovskite through the two-step process, by immersion of the PbI2 film into methylammonium iodide solution, transforms the segregated lead into perovskite. The sputtering technique allows the deposition of uniform films over large areas compatible with roll-to-roll processes, which are desired to produce large-area detectors and perovskite solar cells.

Black-phase formamidinium lead iodide (FAPbI3), with a narrow bandgap and high thermal stability, has emerged as an in-demand material for highly efficient perovskite solar cells (PSCs). In a two-step sequential deposition, the PbI2 film plays an important role in the formation of a perovskite film with desirable qualities. This paper explores using N-methyl-2-pyrrolidone (NMP), a strong Lewis base, and N,N-dimethylformamide (DMF) as a mixed precursor solvent (DMF/NMP) of PbI2 and reports on preparing PbI2 films with a porous morphology by thermal treatment. Porous PbI2 films ensure the diffusion and sufficient reaction of the formamidinium iodide solution to form a smooth perovskite film. In addition, a dynamic spin coating method is also introduced to improve the uniformity of the perovskite film. Both methods yield a pure α-phase FAPbI3 film immediately in the unannealed state, which is necessary for the perovskite film to maintain phase stability. Finally, PSCs with a power conversion efficiency of 21.20% (0.13 cm2) are fabricated and optimized. The unencapsulated PSCs retain 90% of the initial efficiency for 1000 hours in dry air and exhibit a good thermal stability when heated to 85 °C. [ABSTRACT FROM AUTHOR]

Pure‐phase α‐formamidinium lead iodide (α‐FAPbI3) perovskite solar cells (PSCs) possess potential high efficiency because of suitable bandgap. However, achieving high‐quality α‐FAPbI3 films during the spin‐coating process is challenging without anti‐solvent extraction, due to the spontaneous formation of the more stable δ‐FAPbI3 phase and the complexity of multi‐component perovskite precursor solutions. Here a gel precursor with an amorphous structure to eliminate the need for anti‐solvent extraction in achieving the homogeneous and highly oriented pure‐phase α‐FAPbI3 is devised films. The incorporation of N,N′‐dimethylpropyleneurea, and alkylammonium chloride results in extended iodoplumbate clusters in the perovskite precursor solution. In situ, spectroscopic analysis reveals that the emergence of the stable amorphous gel precursor during the initial solidification stage ensures a uniform solute distribution. This effectively prevents preferentially oriented growth in the crystal phase precursor, leading to a significant enhancement in film homogeneity. As a result, power conversion efficiencies of 24.17% for the PSC, and 19.3% for the module are achieved, along with superior operational stability, retaining 96.1% of their initial efficiency after 850 h at the maximum power point tracking. These demonstrate the best performance for the reported pure‐phase α‐FAPbI3 PSCs without anti‐solvent extraction, showing great promise for scalable manufacture. [ABSTRACT FROM AUTHOR]

In this study, the internal and external stabilities of a p–i–n methylammonium lead iodide perovskite solar cell (PSC) are improved. Polystyrene (PS) is introduced into the perovskite layer to form a cross‐linked polymer–perovskite network, which enhances the nucleation and growth of the perovskite grains. Moreover, for the first time, 60 nm thick ZnO/AlOx nanolaminate (NL) thin‐film encapsulation (TFE) is deposited directly on the PSC using an atmospheric‐pressure (AP) spatial atomic layer deposition system operated in AP spatial chemical vapor deposition (AP–SCVD) mode. The rapid nature of AP–SCVD enables encapsulation of the PSCs in open air at 130 °C without damaging the perovskite. The PS additive improves the performance and internal stability of the PSCs by reducing ion migration. Both the PS additive and the ZnO/AlOx NL TFEs improve the external stability under standard test conditions (dark, 65 °C, 85% relative humidity [RH]) by preventing water ingress. The number and thickness of the ZnO/AlOx NL layers are optimized, resulting in a water–vapor transmission rate as low as 5.1 × 10−5 g m−2 day−1 at 65 °C and 85% RH. A 14‐fold increase in PSC lifetime is demonstrated; notably, this is achieved using PS, a commodity‐scale polymer, and AP–SCVD, a scalable, open‐air encapsulation method. [ABSTRACT FROM AUTHOR]

Black-phase formamidinium lead iodide (a-FAPbI3) perovskites are the desired phase for photovoltaic applications, but water can trigger formation of photoinactive impurity phases such as δ-FAPbI3. We show that the classic solvent system for perovskite fabrication exacerbates this reproducibility challenge. The conventional coordinative solvent dimethyl sulfoxide (DMSO) promoted δ-FAPbI3 formation under high relative humidity (RH) conditions because of its hygroscopic nature. We introduced chlorine-containing organic molecules to form a capping layer that blocked moisture penetration while preserving DMSO-based complexes to regulate crystal growth. We report power conversion efficiencies of >24.5% for perovskite solar cells fabricated across an RH range of 20 to 60%, and 23.4% at 80% RH. The unencapsulated device retained 96% of its initial performance in air (with 40 to 60% RH) after 500-hour maximum power point operation. [ABSTRACT FROM AUTHOR]

Understanding the interaction between fullerene (C60) and perovskite surfaces is pivotal for advancing the efficiency and stability of perovskite solar cells. In this study, we investigate the adsorption behavior of C60 on methylammonium lead iodide (MAPbI3) surfaces using periodic density functional theory calculations. We explore various surface terminations and defect configurations to elucidate the influence of surface morphology on the C60‐perovskite interaction, computing the adsorption energy and transfer of charge. Our results reveal distinct adsorption energies and charge transfer mechanisms for different surface terminations, shedding light on the role of surface defects in modifying the electronic structure and stability of perovskite materials. Furthermore, we provide insights into the potential of C60 to passivate surface defects, playing a relevant role in the surface reconstruction after the formation of defects. This comprehensive understanding of C60‐perovskite interactions offers valuable guidelines about the role of fullerenes on surface structure and reconstruction. [ABSTRACT FROM AUTHOR]

Methylammonium Lead Iodide (MAPbI3) has often been known to have a perovskite content and is widely employed in Perovskite Solar Cells (PSCs). However, PSCs suffer from rapid degradation due to their low stability and sensitivity to light, heat, humidity, and air. Hence, this project proposes a two-step spin coat method to synthesize MAPbI3 perovskites in an ambient condition using two different types of solvent (DMF only and a mixture of DMF and DMSO) which were prepared to examine the quality of the perovskite layer. The thin films were characterized to study the structural, optical properties, and surface morphology using XRD, UV-Vis spectroscopy, and SEM. The XRD results show that the perovskite layer prepared using a mixture of DMF and DMSO has a better crystallinity than DMF, even after the sample was kept for two days as the principal peaks confirm the complete formation of MAPbI3 perovskite film. UV-Vis showed that the perovskite layer prepared with the mixture of DMF and DMSO as the solvent has a higher absorbance than the perovskite layer prepared with DMF. The surface morphology of the MAPbI3 films consists of the formation of cubical crystals of uniform size with high compactness, as confirmed by the SEM analysis. However, after two days, both samples showed a degradation providing feedback on the occurred transition to PbI2 due to the contact with moisture and thermal stability. Moreover, the better stability of perovskite films was observed by a two-step than one-step process was demonstrated with comparatively good reproducibility. [ABSTRACT FROM AUTHOR]

We report continuous wave laser-assisted evaporation (CLE), a thin film deposition technique that yields phase-pure and stoichiometric thin films of halide perovskites (HaPs) from stoichiometric HaP targets. We use methylammonium lead bromide (MAPbBr3) to demonstrate the ability to grow with CLE well-oriented and smooth thin films on various substrates. Further, we show the broader applicability of CLE by preparing films of several other 3D HaP compounds, viz., methylammonium lead iodide, formamidinium lead bromide, and a 2D one, butylammonium lead iodide. CLE is a single-source, solvent-free, room-temperature process that needs only roughing pump vacuum; it allows the deposition of hybrid organic-inorganic compound films without needing post-thermal treatment or an additional organic precursor source to yield the intended product. The resulting films are polycrystalline and highly oriented. All these features, and the fact that one stoichiometric source serves as the target, make for an attractive, potentially scalable dry deposition approach. [ABSTRACT FROM AUTHOR]

Organometallic lead halide perovskite powders have gained widespread attention for their intriguing properties, showcasing remarkable performance in the optoelectronic applications. In this study, formamidinium lead iodide (α‐FAPbI3) microcrystals (MCs) is synthesized using retrograde solubility‐driven crystallization. Additionally, methylammonium lead bromide (MAPbBr3) and cesium lead iodide (δ‐CsPbI3) MCs are prepared through a sonochemical process, employing low‐grade PbX2 (X = I & Br) precursors and an eco‐friendly green solvent (γ‐Valerolactone). The study encompasses an analysis of the structural, optical, thermal, elemental, and morphological characteristics of FAPbI3, MAPbBr3, and CsPbI3 MCs. Upon analysing phase stability, a phase transition in FAPbI3 MCs is observed after 2 weeks. To address this issue, a powder‐based mechanochemical method is employed to synthesize stable mixed cation perovskite powders (MCPs) by subjecting FAPbI3 and MAPbBr3 MCs with varying concentrations of CsPbI3. Furthermore, the performance of mixed cation perovskites are examined using the Solar Cell Capacitance Simulator (SCAPS‐1D) software. The impact of cesium incorporation in the photovoltaic characteristics is elucidated. All mixed cation absorbers exhibited optimal device performance with a thickness ranging between 0.6–1.5 µm. It's worth noting that the MCPs exhibit impressive ambient stability, remaining structurally intact and retaining their properties without significant degradation for 70 days of ambient exposure. [ABSTRACT FROM AUTHOR]

The inefficient conversion of lead iodide to perovskite has become one of the major challenges in further improving the performance of perovskite solar cells fabricated by the two‐step method. Herein, the discontinuous lead iodide layer realized by introduction of a polyfluorinated organic diammonium salt, octafluoro‐([1,1′‐biphenyl]‐4,4′‐diyl)‐dimethanaminium (OFPP) iodide which does not form low‐dimensional perovskites, can enable the satisfactory conversion of lead iodide into perovskite, leading to meliorated crystallinity and enlarged grains in the OFPP modulated perovskite (OFPP‐PVK) film. Combined with the effective defect passivation, the OFPP‐PVK films show enhanced charge mobility and suppressed charge recombination. Accordingly, the OFPP‐based perovskite solar cells exhibit a champion efficiency of 24.76 % with better device stability. Moreover, a superior efficiency of 21.04 % was achieved in a large‐area perovskite module (100 cm2). Our work provides a unique insight into the function of organic diammonium additive in boosting photovoltaic performance. [ABSTRACT FROM AUTHOR]

The synergistic utilization of low‐dimensional perovskites with 3D perovskite architectures represents a pervasive approach for fabrication of high‐performance and enduring perovskite solar cells (PSCs). In this work, four distinct ionic liquids (ILs) with distinct cations, were introduced on the surface of 3D perovskite to induce the formation of 1D perovskite.Starting with the analysis of 1D/3D heterojunction structures, the assessment foucsed on the binding energies in four ILs‐induced 1D/3D heterojunctions, comparing electron cloud density within 1D/3D structures, and calculating the formation energies associated with iodine and lead defects within these four 1D/3D perovskite structures via DFT calculations. Furthermore, the time‐resolved grazing‐incidence wide‐angle X‐ray scattering technique, as employed in this study, offers real‐time insights into the phase‐transition occurring during the process of ILs coating and the formation of 1D/3D heterojunctions. The well‐designed and optimized 1D perovskite layer significantly reduces the residual lead iodide (PbI2), modulates the work function of the perovskite, and passivates defects in the 3D perovskite, thereby reducing non‐radiative recombination and enhancing charge transport. With the assistance of 1D/3D hybrid films, we achieved an exceptional power conversion efficiency (PCE) of 24.75% in the generated PSCs with remarkable stability. [ABSTRACT FROM AUTHOR]

We present a design strategy for fabricating ultrastable phase-pure films of formamidinium lead iodide (FAPbI3) by lattice templating using specific two-dimensional (2D) perovskites with FA as the cage cation. When a pure FAPbI3 precursor solution is brought in contact with the 2D perovskite, the black phase forms preferentially at 100°C, much lower than the standard FAPbI3 annealing temperature of 150°C. X-ray diffraction and optical spectroscopy suggest that the resulting FAPbI3 film compresses slightly to acquire the (011) interplanar distances of the 2D perovskite seed. The 2D-templated bulk FAPbI3 films exhibited an efficiency of 24.1% in a p-i-n architecture with 0.5-square centimeter active area and an exceptional durability, retaining 97% of their initial efficiency after 1000 hours under 85°C and maximum power point tracking. [ABSTRACT FROM AUTHOR]