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2D Ruddlesden─Popper (RP) halide perovskites are attracting increasing research interest due to their enhanced stability compared to 3D perovskites. However, the quantum confinement effect of bulk organic spacers hinders the separation and transport of photo‐generated carriers. Here, a multiple aromatic ring spacer, 3‐benzothiophene methylammonium (BTMA), is developed for a new 2D RP perovskite. The BTMA spacer is demonstrated, with a significant dipole moment, can impair the influence of the quantum confinement effect, and the presence of S atoms or thiophene is favorable for enhancing the interaction between organic spacers and inorganic sheets, improving the stability of perovskites. The perovskite photodetector with BTMA as spacers displays higher device performance than the control sample with 1‐naphthalene methylammonium (NMA) as spacers. Importantly, the outstanding stability of BTMA‐based perovskite films and devices is also confirmed under moisture, heat, and illumination conditions. Combining the asymmetric coplanar nanogap electrode architecture, the photodetectors' enhanced responsivity, detectivity, and external quantum efficiency of 314 A W−1, 3.4 × 1013 Jones, and 865%, respectively, are demonstrated. Importantly, the nanogap photodetectors display promising self‐power characteristics, which makes them attractive for numerous energy‐efficient applications. The work highlights a new route toward developing high‐performance 2D RP perovskite‐based photodetectors with excellent long‐term stability. [ABSTRACT FROM AUTHOR]

Although ammonium is the preferred nitrogen source for microbes and plants, in animal cells it is a toxic product of nitrogen metabolism that needs to be excreted. Thus, ammonium movement across biological membranes, whether for uptake or excretion, is a fundamental and ubiquitous biological process catalysed by the superfamily of the Amt/Mep/Rh transporters. A remarkable feature of the Amt/Mep/Rh family is that they are ubiquitous and, despite sharing low amino acid sequence identity, are highly structurally conserved. Despite sharing a common structure, these proteins have become involved in a diverse range of physiological process spanning all domains of life, with reports describing their involvement in diverse biological processes being published regularly. In this context, we exhaustively present their range of biological roles across the domains of life and after explore current hypotheses concerning their evolution to help to understand how and why the conserved structure fulfils diverse physiological functions. [ABSTRACT FROM AUTHOR]

This study examines the structural, optical, and morphological characteristics of Methylammonium lead halide perovskites (MAPbX3) as potential solar cell candidates. Variable band gaps, extended carrier lifetimes, high absorption coefficients, and solution-processable synthesis techniques are among the numerous advantages of these perovskites. The Hot-Injection Method (HIM) is employed in the study to further investigate the unique properties of MAPbX3 perovskites, which is cost-effective and does not require vacuum. MAPbBr3 and MAPbCl3 crystallize in a cubic phase, whereas MAPbI3 crystallizes in a tetragonal phase. The halide versions exhibit morphological differences, with MAPbCl3 exhibiting cubic nanocrystals, MAPbI3 forming a combination of rods and spherical nanocrystals, and MAPbBr3 exhibiting particulate structures. TRPL experiments indicate carrier lifetimes between 1.72 and 7.65 ns, while UV-Vis spectroscopy indicates a blue shift in absorption band edges from MAPbI3 to MAPbCl3. MAPbI3, the most promising candidate for solar cell applications, produces a PCE of 13.66% at a thickness of 250nm, in contrast to MAPbBr3 and MAPbCl3, which produce 6.87% and 4.98% at a thickness of 500nm, respectively. This research establishes a thorough comprehension of the structural, optical, and morphological properties of MAPbX3 perovskites, thereby facilitating the advancement of perovskite solar cell technology and the creation of more cost-effective solar energy solutions. [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]

Organic–inorganic halide perovskites have shown great potential for the conversion of solar energy to hydrogen fuel via photocatalytic reaction due to their excellent optoelectronic properties. However, one of the biggest challenges for organic–inorganic halide perovskite materials in photocatalytic hydrogen evolution reaction (HER) lies in the serious recombination of photogenerated electron and hole pairs. Herein, we reported that the coupling of nickel phosphide (Ni2P) nanoparticles with methylammonium lead halide (MAPbI3) perovskite can significantly enhance the photocatalytic H2 evolution performance of MAPbI3. We found that Ni2P coupling can promote the electron exaction from MAPbI3, thereby accelerating the charge transfer and retarding the charge recombination. Moreover, Ni2P particles exhibited good electrocatalytic activity for the HER. Consequently, the Ni2P/MAPbI3 composite exhibited ca. 459 times higher activity than the parent MAPbI3 in photocatalytic HI splitting reaction. Moreover, the Ni2P/MAPbI3 composite exhibited excellent stability during cycling tests. This work demonstrated the potential of using Ni2P as non-noble metal-based co-catalyst to promote the photocatalytic performance of organic–inorganic halide perovskite. [ABSTRACT FROM AUTHOR]

Solution grown metal halide perovskites (MHPs) are a class of low-cost, direct conversion semiconducting materials with the potential to meet the need for large areas, high stopping power, and high sensitivity x-ray detectors. While polycrystalline MHP thin films have shown significant potential for meeting this need, their efficiencies for detecting x rays are limited by their thickness. This article presents an MHP variant, methylammonium lead tribromide (MAPB) in the form of 3D polycrystalline mosaic wafers with relatively high hole transport properties that demonstrated stable sensitivity during irradiation. An expedited and efficient detector fabrication method that did not include polishing or sintering was evaluated, and a radiograph of a brass key was produced using electron collection from the resulting wafer. However, a high dose rate was required due to very low sensitivity values. The effects of surface inhomogeneity and radiation damage were investigated as explanatory factors, and these phenomena were further characterized through IV measurements, current response as a function of electric field and x-ray dose rate, and alpha particle irradiation. The results indicated that although compromising surface quality for fabrication efficiency was the primary hindrance to the x-ray detection performance of 3D polycrystalline MAPB, stable performance could still be achieved under reasonable dose rates. [ABSTRACT FROM AUTHOR]

We present an experimental investigation of methylammonium lead tribromide single crystals in the orthorhombic, tetragonal, and cubic phases based on inelastic and deep inelastic neutron scattering experiments. We show how the average hydrogen nuclear kinetic energy, mainly affected by zero-point vibrational energies, shows differences larger compared to the changes simply related to temperature effects when moving from one phase to another. In particular, the Gaussian contribution to the average nuclear kinetic energy is larger in the tetragonal phase compared to the cubic and orthorhombic ones. Moreover, we find that the vibrational densities of states of MAPbBr3 single crystals in the orthorhombic phase are compatible with previously reported results on powder samples, and that the only vibrational modes that show slightly different frequencies compared to MAPbI3 are those in the energy range between 100 and 300 cm−1, related to librational/rotational modes. As these shifts are of about 10 cm−1 and do not affect any higher-energy vibrational mode, we conclude that the zero-point energies and average nuclear kinetic energies in the two-hybrid organic/inorganic perovskites are expected to be approximately the same within a harmonic framework. [ABSTRACT FROM AUTHOR]

This study focuses on improving the quality of MAPbI3‐based perovskite films by adjusting the concentration ratios of the methylammonium iodide (MAI) precursor using a two‐step sequential deposition method. The primary objective is to explore how altering the MAI concentration influences the microstrain, dislocation density, perovskite film quality, and their subsequent impact on the performance of perovskite solar cells. The examined device configuration CdS/MAPbI3/Spiro‐OMeTAD demonstrates impressive power conversion efficiency of 12.05%, Voc of 1.02 V, Jsc of 16.2 mA cm−2, and fill factor of 0.73. X‐ray diffraction and scanning electron microscope analyses show improved crystal quality and surface characteristics with reduced microstrain, dislocation density, larger crystal grains, and minimized pinholes. The investigation of MAPbI3's optical and electrical characteristics provides in‐depth insights, facilitating the optimization of MAI precursor concentrations for improved perovskite film development and enhanced solar cell performance. [ABSTRACT FROM AUTHOR]

Surface/interface engineering of methylammonium lead bromide (MAPbBr3) single crystals (SCs) is crucial for carrier generation/recombination, separation, and transportation, thereby enabling superior optoelectronics. Herein, a surface‐engineered crystallization technique is presented in which a thin polycrystalline MAPbBr3 layer is in situ grown on the surface of bulk mm‐sized MAPbBr3 SCs. The growth direction and the atomic distribution of both the polycrystalline surface layer and the single crystalline core have been analyzed by damage‐free atomic‐resolution transmission electron microscopy (TEM). The polycrystalline nature of the crystals gives rise to bright green emission under UV light. Scanning probe microscopy results show that the current at the emissive MAPbBr3 film/MAPbBr3 SC surface is five times higher than that at a non‐emissive surface when illuminated. Lateral photodetectors based on MAPbBr3 film/MAPbBr3 SCs can achieve excellent detectivities (≈1013 Jones) and high photoresponsivities (≈20 A W−1). Furthermore, a semiconductor‐based fluorescence quick response (FQR) code is patterned on the same bright green‐emitting surface of the MAPbBr3 film/MAPbBr3 SC using a picosecond laser pulse, with a scalability of 3 × 3 mm2. An FQR code integrated with a photodetector may serve as a potential double security tag in bank cards, passports, door security, etc. [ABSTRACT FROM AUTHOR]

Nowadays, methylammonium tin iodide MASnI 3 halide-based perovskite solar cells are engaging the research community, because of its unique properties like excellent light absorption, narrow band gap, etc. Until now, 7.1% highest power conversion efficiency (PCE) is reported for MASnI 3 perovskite solar cells (PSCs). The focus of the research is the design and analysis of lead-free tin-halide-based perovskite solar using SCAPS TCAD tool. Moreover, the proposed device is analyzed by consider some parameters such as absorber layer thickness, variations of different electron transport layer (ETL) and hole transport layer (HTL) and thickness variation of ETL and HTL. In this work, 12.76% highest power conversion efficiency is attained by the optimized device. Furthermore, the focused research work could be consider for climatic conditions analysis, fabrication opportunities and tandem applications. [ABSTRACT FROM AUTHOR]

Point defects in methylammonium lead iodide (MAPbI3) are believed to be the source of its room-temperature ferromagnetic behavior. The existence of room-temperature ferromagnetism observed through the hysteresis in the M-H (magnetization vs. magnetic field) curve proves that ferromagnetism is possible even at room temperature in the tetragonal phases of MAPbI3 system. Employing positron annihilation spectroscopy, the presence of a significant amount of point defects in the ball-mill ground MAPbI3 sample has been identified. Coincidence Doppler broadening spectroscopy identifies that the point defects are mostly iodine vacancy (V˙I) in MAPbI3. Experimental data supports the theoretical prediction of iodine vacancy (V˙I)-induced ferromagnetism in the cubic phase which exists at a little higher temperature than the room-temperature tetragonal phase for MAPbI3. Moreover, the ab-initio band structure calculation shows the n-/p-type semiconducting behavior due to the vacancy formation in MAPbI3. Ferromagnetism along with semiconducting properties makes it viable for spintronics applications. [ABSTRACT FROM AUTHOR]

(CH3NH3)2PdSe16, tetragonal, P 4 ‾ b 2 (no. 117), a = 12.7821(4) Å, c = 7.1123(2) Å, V = 1162.02(8) Å3, Z = 2, Rgt(F) = 0.0306, wRref(F2) = 0.0841, T = 223 K. [ABSTRACT FROM AUTHOR]

(CH3NH3)2PdSe16, tetragonal, P 4 ‾ b 2 (no. 117), a = 12.7821(4) Å, c = 7.1123(2) Å, V = 1162.02(8) Å3, Z = 2, Rgt(F) = 0.0306, wRref(F2) = 0.0841, T = 223 K. [ABSTRACT FROM AUTHOR]

In this work, our aim was to design and numerical simulation of a solar cell using the SCAPS-1D simulation program. The studied solar cell has an N-I-P type structure, with its active layer based on a hybrid (organic–inorganic) semiconductor called "methylammonium tin triiodide perovskite", CH3NH3SnI3, which is known as MASnI3. This semiconductor is known for its efficiency in the field of photovoltaic thanks to its good properties such as high absorption, direct bang-gap, and facilities of elaboration. The objective of this study was primarily focused on improving the performance of the perovskite solar cells, specifically enhancing their reproducibility and stability, as they tend to degrade rapidly. To achieve this, we proposed the use of ZnO and Spiro-OMeTAD as charge transport layers (ETL and HTL, respectively) and varying the thickness of the active layer to obtain the optimal parameters that ensure the proper functioning of the cell. [ABSTRACT FROM AUTHOR]

The addition of copper bromide to the perovskite precursor solutions increased the conversion efficiencies of the devices. On the other hand, the short-circuit current densities decreased with an increase in the added amounts of copper (Cu). From first-principles calculations, the partial substitution of lead with Cu resulted in the formation of a Cu d orbital energy level in the forbidden band, which worked as a recombination center, causing the generated carriers to disappear. Experiments and calculations show the effects of Cu substitution on the electronic structures and the ability of the addition of Cu compounds to further improve the device performance. [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrid perovskite materials continue to attract significant interest due to their optoelectronic application. However, the degradation phenomenon associated with hybrid structures remains a challenging aspect of commercialization. To overcome the stability issue, we have assembled the methylammonium lead bromide nano islands (MNIs) on the backbone of poly-3-dodecyl-thiophene (PDT) for the first time. The structural and morphological properties of the MNI-PDT composite were confirmed with the aid of X-ray diffraction (XRD) studies, Field emission scanning electron microscope (FESEM), and X-ray photoelectron spectroscopy (XPS). The optical properties, namely absorption studies, were carried out by ultraviolet-visible spectroscopy. The fluorescent behavior is determined by photoluminescence (PL) spectroscopy. The emission peak for the MNI-PDT was observed at 536 nm. The morphology studies supported by FESEM indicated that the nano islands are completely covered on the surface of the polymer backbone, making the hybrid (MNI-PDT) stable under environmental conditions for three months. The interfacial interaction strategy developed in the present work will provide a new approach for the stabilization of hybrids for a longer time duration. [ABSTRACT FROM AUTHOR]

The interest in highly luminescent organic-inorganic hybrid perovskite, methylammonium lead bromide (MLB) nanocrystals (NCs) has grown significantly due to their many applications in optoelectronics. However, the biggest hurdle has been the effective use of the materials in large optoelectronic applications and their poor stability in various environmental conditions. To address the problem of the poor stability of highly luminescent MLB nanostructures, we synthesized MLB NCs on the surface of cellulose nanofibers (CNF) for the first time. The synthesized (MLB@CNF) composite shows green emission peak at 529 nm. The scanning electron microscopy images confirm that perovskite NCs are well attached to the surface of cellulose nanofiber. These composite materials offer improved stability and luminescent features in moist environments for over six months. The developed interfacial interaction strategy will provide a novel approach to obtain durable nanocrystals using cellulose-based materials. [ABSTRACT FROM AUTHOR]

Here, we have synthesized methylammonium based two metal halide perovskites (MHP) such as MAPbBr3, and MAPbI3 using methylammonium bromide, methylammonium iodide, lead bromide, respective at room temperature under certain experimental conditions. All synthesized MHPs have been confirmed through X-ray diffraction technique (XRD), scanning electron microscope (SEM), Fourier transform infra-red (FTIR) and photoluminescence (PL) analysis. Afterward, comparative evaluation on optical sensing capability has been made for both MHPs using PL in different solvents. Importantly, we find out that MAPbBr3 exhibit an excellent optical feature over MAPbI3 in hexane only. Afterward, MAPbBr3 has also been explored to know the sensing capability for nitrobenzene sensing. Our model study confirms that MAPbBr3 is an excellent sensing material with R square (0.87), selectivity (16.9%) and Stern Volmer constant (Ksv=10− 2 × 0.464) for nitrobenzene in hexane. [ABSTRACT FROM AUTHOR]

We have fabricated planar interdigitated photodetectors exhibiting high responsivity. These detectors are based on thin layers of methylammonium lead bromide (MAPbBr3) at 90 nm thickness. MAPbBr3 thin films were first characterized on glass (borosilicate) substrates using absorption and photoluminescence measurements showing a high absorption edge at 521 nm and strong emission at 530 nm, as expected. MAPbBr3 thin films were then deposited on top of interdigitated electrodes, hence producing planar photodetectors with responsivity up to 0.4 A/W. Such higher performances were attributed to the interdigitated design, low crack density (0.05 µm−2), and lower resistivity (20 MΩ.cm) compared to MAPbBr3 single crystal. Therefore, this work highlights MAPbBr3 thin films as very promising for photodetection applications. [ABSTRACT FROM AUTHOR]

The field of hybrid organic–inorganic perovskite materials continues to attract the interest of the scientific community due to their fascinating properties and the plethora of promising applications in photovoltaic and optoelectronic devices. To enhance the efficiency and stability of perovskite-based devices, it is essential to discover novel compounds but also to investigate their various physicochemical, structural, and thermal properties. In this work, we report the synthesis and structural characterization of two novel hybrid lead bromide perovskites, combining the imidazolium cation (IMI) with methylammonium (MA) or formamidinium (FA) cations. The isolated polycrystalline powders were studied with X-ray powder diffraction (XPRD) and were formulated as (IMI)(MA)Pb2Br6, a 3D structure consisting of dimers of face-sharing octahedra linked in corner-sharing mode, and (IMI)(FA)PbBr4, a 2D (110) oriented layer structure with zig-zag corner-sharing octahedra. The thermal stability of (IMI)(MA)Pb2Br6 and (IMI)(FA)PbBr4 was investigated with thermogravimetric (TG) and differential scanning calorimetry (DSC) experiments which showed that both compounds are chemically stable (at least) up to 250 °C. Variable-temperature X-ray diffractometric (VT-XRD) studies of (IMI)(FA)PbBr4 highlighted a structural modification occurring above 100 °C, that is a phase transformation from triclinic to orthorhombic, via an elusive monoclinic phase.

Methylammonium lead iodide (CH3NH3PbI3) is one of the most attractive materials for optoelectronic applications, and it is the most typical absorber in perovskite solar cells, which are unprecedentedly successful devices in terms of power conversion efficiency. In this work, the conductivity and capacitance spectra of symmetrically contacted Au/CH3NH3PbI3/Au thick pellets are measured via impedance spectroscopy at different temperatures in dark equilibrium. The experimental conductivity spectra are parameterized and showed to follow the formalism of hopping DC conductivity in the CH3NH3PbI3 bulk. The presence of several regimes for the general Jonscher's "universal" conductivity-frequency response is highlighted and associated with the ionic-electronic overlapping conductivities. For the capacitance spectra, the general features of electrode polarization capacitance at the CH3NH3PbI3/Au interfaces are identified but yet are found to be in disagreement with some trends of classical ionic conductivity models, unable to separate different contributions. Accordingly, an analytical model is proposed accounting for hopping processes where the low frequency activation energy is split into ionic and electronic components. Our parameterizations and analytical model discern between the bulk/interface and ionic/electronic phenomena and estimate the multiple activation energies in this hybrid halide perovskite. [ABSTRACT FROM AUTHOR]

Methylammonium lead iodide (CH3NH3PbI3) is one of the most attractive materials for optoelectronic applications, and it is the most typical absorber in perovskite solar cells, which are unprecedentedly successful devices in terms of power conversion efficiency. In this work, the conductivity and capacitance spectra of symmetrically contacted Au/CH3NH3PbI3/Au thick pellets are measured via impedance spectroscopy at different temperatures in dark equilibrium. The experimental conductivity spectra are parameterized and showed to follow the formalism of hopping DC conductivity in the CH3NH3PbI3 bulk. The presence of several regimes for the general Jonscher's "universal" conductivity-frequency response is highlighted and associated with the ionic-electronic overlapping conductivities. For the capacitance spectra, the general features of electrode polarization capacitance at the CH3NH3PbI3/Au interfaces are identified but yet are found to be in disagreement with some trends of classical ionic conductivity models, unable to separate different contributions. Accordingly, an analytical model is proposed accounting for hopping processes where the low frequency activation energy is split into ionic and electronic components. Our parameterizations and analytical model discern between the bulk/interface and ionic/electronic phenomena and estimate the multiple activation energies in this hybrid halide perovskite. [ABSTRACT FROM AUTHOR]

Methylammonium (MA)-free perovskite solar cells (PVSCs) have obtained great attention recently, owing to their superior stability. However, there are still gaps in efficiency between MA-free PVSCs and MA-containing counterparts. Their stability still needs to be further enhanced for meeting commercial standards, especially the illumination stability. Here, we incorporate Zn2+ into perovskite thin films to passivate defects, successfully achieving a champion efficiency of 20.7% and reinforcing the stability of MA-free FA0.9Cs0.1PbI3 PVSCs. This study reveals that Zn-doping can increase the grain size and contribute to modulate the crystallization process. Moreover, it is found that most of the Zn2+ aggregates at the grain boundaries passivating defects and, thus, effectively restrain the non-radiative recombination in the PVSCs. These findings provide a new way of realizing highly efficient and stable PVSCs. [ABSTRACT FROM AUTHOR]

Isostructural series of CH3NH3Pb(1 − x)SnxCl3 (x = 0%, 0.5%, 2.5%, 10%, 20%, and 33%) perovskites are prepared by the solution processing method. The synthesized perovskites are investigated in terms of their structural, optoelectronic, morphological, elemental, and thermal properties. The improved crystallinity and enhanced absorption edge toward longer wavelength are observed due to the increased amount of tin (Sn) in the Pb site of CH3NH3PbCl3. The bandgap is reduced from 2.93 eV to 2.83 eV when one third atomic percentage (at. %) of Pb is replaced with Sn. Further, elemental analysis confirms the successful doping of Sn in the host perovskite without the presence of any impurity. The thermogravimetric study of the prepared samples shows that the thermal stability is improving up to 20 at. % Sn doping, whereas the stability starts deteriorating for 33 at. % doping. The obtained results reveal that less toxic, better crystallinity, enhanced optoelectronic properties can be achieved by partial doping of Sn in CH3NH3Pb(1 − x)SnxCl3 perovskites. This work offers a new reference for exploring the use of Sn-doped CH3NH3PbCl3 perovskite materials in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Inspired by its great success in the photovoltaic field, methylammonium lead iodide perovskite (MAPbI3) has recently been actively explored as photocatalysts in H2 evolution reactions. However, the practical application of MAPbI3 photocatalysts remains hampered by the intrinsically fast trapping and recombination of photogenerated charges. Herein, we propose a novel strategy of regulating the distribution of defective areas to promote charge‐transfer dynamics of MAPbI3 photocatalysts. By deliberately designing and synthesizing the MAPbI3 photocatalysts featuring a unique continuation of defective areas, we demonstrate that such a feature enables retardation of charge trapping and recombination via lengthening the charge‐transfer distance. As an outcome, such MAPbI3 photocatalysts turn out to achieve an impressive photocatalytic H2 evolution rate as high as 0.64 mmol ⋅ g−1 ⋅ h−1, one order of magnitude higher than that of the conventional MAPbI3 photocatalysts. This work establishes a new paradigm for controlling charge‐transfer dynamics in photocatalysis. [ABSTRACT FROM AUTHOR]

We study the low-temperature (T = 4.7 K) emission dynamics of a thin film of methylammonium lead bromide (MAPbBr 3 ), prepared via the anti-solvent method. Using intensity-dependent (over 5 decades) hyperspectral microscopy under quasi-resonant (532 nm) continuous wave excitation, we revealed spatial inhomogeneities in the thin film emission. This was drastically different at the band-edge (∼550 nm, sharp peaks) than in the emission tail (∼568 nm, continuum of emission). We are able to observe regions of the film at the micrometer scale where emission is dominated by excitons, in between regions of trap emission. Varying the density of absorbed photons by the MAPbBr 3 thin films, two-color fluorescence lifetime imaging microscopy unraveled the emission dynamics: a fast, resolution-limited (∼200 ps) monoexponential tangled with a stretched exponential decay. We associate the first to the relaxation of excitons and the latter to trap emission dynamics. The obtained stretching exponents can be interpreted as the result of a two-dimensional electron diffusion process: Förster resonant transfer mechanism. Furthermore, the non-vanishing fast monoexponential component even in the tail of the MAPbBr 3 emission indicates the subsistence of localized excitons. Finally, we estimate the density of traps in MAPbBr 3 thin films prepared using the anti-solvent method at n∼10 17 cm − 3 . [ABSTRACT FROM AUTHOR]

Cesium methylammonium lead iodide (CsxMA1−xPbI3) nanocrystals were obtained with a wide range of A‐site Cs‐MA compositions by post‐synthetic, room temperature cation exchange between CsPbI3 nanocrystals and MAPbI3 nanocrystals. The alloyed CsxMA1−xPbI3 nanocrystals retain their photoactive perovskite phase with incorporated Cs content, x, as high as 0.74 and the expected composition‐tunable photoluminescence (PL). Excess methylammonium oleate from the reaction mixture in the MAPbI3 nanocrystal dispersions was necessary to obtain fast Cs‐MA cation exchange. The phase transformation and degradation kinetics of films of CsxMA1−xPbI3 nanocrystals were measured and modeled using an Avrami expression. The transformation kinetics were significantly slower than those of the parent CsPbI3 and MAPbI3 nanocrystals, with Avrami rate constants, k, at least an order of magnitude smaller. These results affirm that A‐site cation alloying is a promising strategy for stabilizing iodide‐based perovskites. [ABSTRACT FROM AUTHOR]

Organic–inorganic halide perovskites (HOIPs) are promising light-electric conversion materials for optoelectronic devices. Improving the light responsiveness properties of HOIPs is of great significance for the development of the optoelectronics industry. In this study, we have investigated the effect of pressure on the optoelectronics properties of the archetypical representative HOIPs methylammonium lead iodide nanoplates. An enhancement of the photocurrent accompanied by 4 times-prolonged carrier lifetime, enhanced photoluminescence (PL) intensity, and narrowed bandgap were observed via applying pressure to about 0.36 GPa, while these physical properties got worse with further compression. Strikingly, when released to ambient conditions, the photocurrent is further increased to 4.5 times and the carrier lifetime is prolonged to 1.5 times of the corresponding values for an initial sample, while the bandgap slightly blueshifted and the PL intensity slightly reduced. These results suggest that the increased photocurrent may be related to the increased carrier lifetime of the quenched sample, which gives more time for the separation of photoelectrons from vacancies before recombination. This study demonstrated that pressure engineering can be a real possibility for improving the light responsiveness of the HOIPs material in practical applications. [ABSTRACT FROM AUTHOR]

The structural stability of the extensively studied organic–inorganic hybrid methylammonium tetrel halide perovskite semiconductors, MATtX3 (MA = CH3NH3+; Tt = Ge, Sn, Pb; X = Cl, Br, I), arises as a result of non-covalent interactions between an organic cation (CH3NH3+) and an inorganic anion (TtX3−). However, the basic understanding of the underlying chemical bonding interactions in these systems that link the ionic moieties together in complex configurations is still limited. In this study, ion pair models constituting the organic and inorganic ions were regarded as the repeating units of periodic crystal systems and density functional theory simulations were performed to elucidate the nature of the non-covalent interactions between them. It is demonstrated that not only the charge-assisted N–H···X and C–H···X hydrogen bonds but also the C–N···X pnictogen bonds interact to stabilize the ion pairs and to define their geometries in the gas phase. Similar interactions are also responsible for the formation of crystalline MATtX3 in the low-temperature phase, some of which have been delineated in previous studies. In contrast, the Tt···X tetrel bonding interactions, which are hidden as coordinate bonds in the crystals, play a vital role in holding the inorganic anionic moieties (TtX3−) together. We have demonstrated that each Tt in each [CH3NH3+•TtX3−] ion pair has the capacity to donate three tetrel (σ-hole) bonds to the halides of three nearest neighbor TtX3− units, thus causing the emergence of an infinite array of 3D TtX64− octahedra in the crystalline phase. The TtX44− octahedra are corner-shared to form cage-like inorganic frameworks that host the organic cation, leading to the formation of functional tetrel halide perovskite materials that have outstanding optoelectronic properties in the solid state. We harnessed the results using the quantum theory of atoms in molecules, natural bond orbital, molecular electrostatic surface potential and independent gradient models to validate these conclusions. [ABSTRACT FROM AUTHOR]

CH3NH3PbI3 perovskite solar cells using metal phthalocyanines (MPcs) with decaphenylcyclopentasilane (DPPS) are fabricated and characterized. The effect of addition of MPcs on the photovoltaic properties is investigated by changing the central element of the MPc and depositing MPc and DPPS successively on the perovskite layer. When silicon phthalocyanine is used to the cell, the microstructure of the perovskite film improves, which results in improvement of the open‐circuit voltage, fill factor, and photoconversion efficiency. For cells with only MPcs as the hole‐transport layer, the conversion efficiency increases by passivation with the phthalocyanine and crystal growth at room temperature. [ABSTRACT FROM AUTHOR]

Hybrid halocuprates(I) are nowadays the subject of intensive studies as promising materials for various optoelectronic applications. This class of materials is characterized by wide structural diversity enabled by a great variety in the size and shape of organic cations. Therefore, the study of composition–structure–property relationships is a key step for the rational design of new halocuprate materials with desired properties. In this paper, we comprehensively studied MABr/CuBr and FABr/CuBr systems (MA+ = methylammonium and FA+ = formamidinium) and established the existence of five novel phases (namely, MACu2Br3, FA2[Cu4Br6], MACuBr2, FACuBr2, and FA3CuBr4) related to four different structural types and three distinct A+ : Cu+ stoichiometries (A+ = MA+/FA+). The optical properties of the discovered phases are studied by absorption and low-temperature photoluminescence spectroscopy. Based on a crystal–chemical analysis, we explained a unique structural diversity of the MA- and FA-based bromocuprates, as well as revealed new structure–property relationships. [ABSTRACT FROM AUTHOR]

The field of hybrid organic–inorganic perovskite materials continues to attract the interest of the scientific community due to their fascinating properties and the plethora of promising applications in photovoltaic and optoelectronic devices. To enhance the efficiency and stability of perovskite-based devices, it is essential to discover novel compounds but also to investigate their various physicochemical, structural, and thermal properties. In this work, we report the synthesis and structural characterization of two novel hybrid lead bromide perovskites, combining the imidazolium cation (IMI) with methylammonium (MA) or formamidinium (FA) cations. The isolated polycrystalline powders were studied with X-ray powder diffraction (XPRD) and were formulated as (IMI)(MA)Pb2Br6, a 3D structure consisting of dimers of face-sharing octahedra linked in corner-sharing mode, and (IMI)(FA)PbBr4, a 2D (110) oriented layer structure with zig-zag corner-sharing octahedra. The thermal stability of (IMI)(MA)Pb2Br6 and (IMI)(FA)PbBr4 was investigated with thermogravimetric (TG) and differential scanning calorimetry (DSC) experiments which showed that both compounds are chemically stable (at least) up to 250 °C. Variable-temperature X-ray diffractometric (VT-XRD) studies of (IMI)(FA)PbBr4 highlighted a structural modification occurring above 100 °C, that is a phase transformation from triclinic to orthorhombic, via an elusive monoclinic phase. [ABSTRACT FROM AUTHOR]

In this study, a thin film of methylammonium lead iodide (MAPbI3) was employed as the switching layer in the metal/MAPbI3/FTO devices. Two metals, Ag and Cr, were used as active and inert top electrodes to govern the hysteresis effect of memory devices, respectively. While the Cr/MAPbI3/FTO device displayed an analog resistive switching (RS) behavior and a comparatively low ON/OFF ratio of 10, the Ag/MAPbI3/FTO structure displayed digital bipolar RS and a high ON/OFF ratio of 102. The density functional theory simulations suggest that these various behaviors may be caused by variations in the mutual interaction between the iodine vacancy defect and the metal contact properties. The SET process involved switching both devices from a high-resistance state to a low-resistance one using the space charge-limited current mechanism. In the RESET process, the Ag-electrode device is allocated the Poole–Frenkel emission mechanism, and the Cr-electrode device is followed the Fowler–Nordheim tunneling mechanism. The formation and dissociation of iodine vacancy filaments via the dielectric layer were identified as the RS mechanism in both devices. The findings show that organic–inorganic hybrid perovskite has a strong potential for data storage. [ABSTRACT FROM AUTHOR]

[Display omitted] • CH 3 NH 3 PbI 3 perovskite degradation was observed for three days interval until film gets fully degradation. • The Copper iodide (CuI) was employed as hole transport layer for device study. • Phase change, element exclusion, surface changes electrical changes was observed during the degradation. • Degradation based impedance changes observed and discussed. • Degradation behaves differently with device and single layer. Methylammonium lead iodide (MAPbI 3) has attracted more attention due to its promising features appropriate for photovoltaic application, although the material still struggles with instability towards environmental factors. Understanding the degradation mechanism in this material is of immense importance in increasing material stability. This work investigated the degradation process of MAPbI 3 perovskite in an ambient atmosphere with controlled humidity for twelve days at three days interval. The crystallographic structural changes were observed by X-Ray Diffraction (XRD) and analyzed with the support of the Rietveld refinement method. The result shows transition from MAPbI 3 Tetragonal to PbI 2 trigonal by removal of CH 3 NH 3 I, which is evident in X-ray photoelectron spectroscopy (XPS) elemental analysis. UV–Vis spectroscopy and photoluminescence show changes in the band-gap. Scanning electron microscopy (SEM) observes morphological changes and impedance spectroscopy studies electrical behavior. Our study explains the MAPbI 3 structural, optical, morphological, thermal, and electrical behavior changes during degradation in different studies; it is beneficial for a deeper understanding of the degradation mechanism. [ABSTRACT FROM AUTHOR]

Materials engineering is key to improving the stability and photovoltaic parameters of inverted perovskite solar cells (PSCs). This work presents the effect of two different fluorinated additives on the performance of PSCs containing the archetypal three‐dimensional perovskite, methylammonium lead triiodide (MAPbI3). 3‐(2,3,4,5,6‐Pentafluorophenyl)propylammonium iodide (FPAI) is added to the anode modifying layer and (2,3,4,5,6‐pentafluorophenyl)methylammonium bromide (FMABr) is blended into the perovskite layer. The inverted devices containing FPAI in the anode modifying layer and 0.32 mol% of FMABr from the perovskite precursor solution had hysteresis‐free current density‐voltage characteristics and a maximum power conversion efficiency of 22.3%, which is an absolute increase of 1.7% compared to the MAPbI3 device (20.6%) of the same architecture but without the additives. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PeSCs) have been introduced as a new photovoltaic device due to their excellent power conversion efficiency (PCE) and low cost. However, due to the limitations of the perovskite film itself, the existence of defects was inevitable, which seriously affects the number and mobility of carriers in perovskite solar cells, thus restricting PeSCs improved efficiency and stability. Interface passivation to improve the stability of perovskite solar cells is an important and effective strategy. Here, we use methylammonium halide salts (MAX, X = Cl, Br, I) to effectively passivate defects at or near the interface of perovskite quantum dots (PeQDs)/triple-cation perovskite films. The MAI passivation layer increased the open circuit voltage of PeQDs/triple-cation PeSC by 63 mV up to 1.04 V, with a high short-circuit current density of 24.6 mA cm−2 and a PCE of 20.4%, which demonstrated a significant suppression of interfacial recombination. [ABSTRACT FROM AUTHOR]

We have investigated the effects of the methylammonium bromide (MABr) content of the precursor solution on the properties of wide-bandgap methylammonium lead tribromide (MAPbBr3) perovskite solar cells (PSCs). In addition, the anti-solvent process for fabricating MAPbBr3 perovskite thin films was optimized. The MAPbBr3 precursor was prepared by dissolving MABr and lead bromide (PbBr2) in N,N-dimethylformamide and N,N-dimethyl sulfoxide. Chlorobenzene (CB) was used as the anti-solvent. We found that both the morphology of the MAPbBr3 layer and the PSCs performance are significantly affected by the MABr content in perovskite precursor solution and anti-solvent dripping time. The best-performing device was obtained when the molar ratio of MABr:PbBr2 was 1:1 and the CB drip time was 10 s. The best device exhibited a power conversion efficiency of 7.58%, short-circuit current density of 7.32 mA·cm−2, open-circuit voltage of 1.30 V, and fill factor of 79.87%. [ABSTRACT FROM AUTHOR]

Perovskite nanostructures are ideal model systems for fundamental studies and as convenient building blocks for proof-of-principle studies of optoelectronic device design and improvemen.Methylammonium lead iodide (CH3NH3PbI3) and some other perovskites have drawn significant attention to the science community because of their high power conversion efficiency in solar cells. In addition, this group of semiconductors has the potential to be used in a wide range of optoelectronic devices like light-emitting diodes, lasers, field-effect transistors, photodetectors, photoluminescent, electroluminescent devices as well as light-emitting electrochemical cells. Commercialization of perovskite materials may revolutionize the global energy sector as these materials are abundant in nature and inexpensive, as a result it would be cheaper and more efficient than silicon-based technology. However, the insufficient long-term stability and toxicity of lead (Pb) are two major barriers for Pb-based hybrid perovskites to be adopted in large-scale industrial applications. Therefore, it is almost important to find non-toxic Pb-free stable perovskites for the further development of perovskites based optoelectronic technology. A detailed atomistic insight of the fundamental properties of perovskite materials can help to understand the basic characteristics of the materials and it can guide research to find non-toxic stable materials for photovoltaics and optoelectronics. Among these candidates, Sn-based perovskites have attracted the most attention due to their very similar properties, and the most promising performance achieved by their devices. This article presents investigations of the structural, electronic, optical and mechanical properties based organic-inorganic metal halid perovskites (MABI3) (B = Pb, Sn). [ABSTRACT FROM AUTHOR]

Here, we investigate in detail the impact of the size of the methylammonium iodide (MAI) reactants in the mechanochemical powder synthesis of the halide perovskite methylammonium lead iodide (MAPbI3). Morphology and structural characterizations by scanning electron microscopy and X‐ray diffraction reveal that with increasing MAI reactant size, the particle size of the perovskite powder increases, while its defect density decreases, as suggested by nuclear quadrupole resonance spectroscopy and photoluminescence investigations. The reason for this behavior seems to be associated to the sensitive influence of the MAI size on the time durations of MAPbI3 synthesis and delayed MAPbI3 crushing stage during ball milling. Thus, our results emphasize the high importance the reactant properties have on the mechanochemical synthesis of halide perovskites and will contribute to enhance the reproducibility and control of the fabrication of halide perovskites in powder form. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid perovskite solar cells have the advantage of being able to implement a high conversion efficiency, easy fabrication process and low cost to commercial products of photovoltaic devices. The perovskite solar cells have a photovoltaic performance with reduced durability due to the volatility of organic cations and toxic lead in the perovskite crystal as an active layer. The purpose of this research is to investigate the effect of additives such as cupper chloride and potassium iodide in the perovskite crystal on the photovoltaic properties and electronic structure. The distribution of 3d orbital of cupper ion conjugated with 5p orbital of iodine ion at the valence band, and 6p orbital of lead ion at the conduction band, influences the charge generation and transfer, as well as the carrier mobility with a narrowing band gap. The addition of potassium iodide delocalizes the charge distribution near the cupper, iodide, and lead ions, which promotes the charge generation and carrier diffusion, yielding an increase in the short circuit current density relating to the conversion efficiency. [ABSTRACT FROM AUTHOR]

Herein, MACl post-treatment is utilized for MAPbI3 and (Cs0.05FA0.79MA0.16)Pb(I0.84Br0.16)3 (MA, methylammonium; FA, formamidinium). Photoluminescence of both perovskite films exhibits a peak shift to the higher emission energy as well as a slower decay of recombination by the MACl treatment, suggesting the passivation of defects in band tail states. Photovoltaic performance is further correlated with the change of deep electronic traps in the bandgap, which is characterized through capacitance analyses of solar cells. Degradation of MAPbI3 cells by the MACl treatment is attributed to the additional deep-trap formation, and the improvement of photovoltaic parameters for triple-cation perovskites is correlated with the reduction of deep traps with trap-level shifts toward the band edge. The reactive characters of MAPbI3 against post-treatment conditions seem to be responsible for the deep-trap formation as evidenced by the microstructural/morphological results, and consequently, the improved resistance to trap the formation of triple-cation perovskites provides viability for further performance enhancement by surface passivation. [ABSTRACT FROM AUTHOR]

Methylammonium lead iodide (MAPbI3) has been emerged out as an efficient perovskite absorber material in solar cell applications and extensively studied on both experimental and theoretical fronts. However, these MAPbI3-based perovskite solar cells (PSCs) undergo degradation due to thermal instability of MAPbI3, which in-turn deteriorates the performance of PSC for a long-run. In this work, we deal with the computational analysis of mixed-halide MAPb(I1-xClx)3 based PSCs by changing hole transport layers (HTLs) so that higher efficiency can be aimed. It has been observed that not only the appropriate band alignment of HTL with perovskite, but the mobility of HTL also play a pivotal role in achieving the better photovoltaic (PV) performance. Furthermore, it is noteworthy that Cu2O exhibits a better PV performance in contrast to other HTLs considered in our study. Thus, the present simulation work paves a path for the experimentalists to design similar PSCs by cutting-down the cost of experimental trials. [ABSTRACT FROM AUTHOR]

Solution processed thin film organic-inorganic perovskites are key to the large scale manufacturing of next generation wafer scale solar cell devices. The high efficiency of the hybrid perovskite solar cells is derived mainly from the large carrier mobility and the charge dynamics of films, which heavily depend on the type of solvent used for the material preparation. Here, we investigate the nature of conduction and charge carrier dynamics of mixed organic-inorganic cations [methylammonium (MA), formamidinium (FA), and cesium (Cs)] along with the mixed halides [iodine (I) and bromine (Br)] perovskite material [Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3] synthesized in different solvents using optical pump terahertz probe (OPTP) spectroscopy. Our findings reveal that carrier mobilities and diffusion lengths strongly depend on the type of solvent used for the preparation of the mixed cation perovskite film. The mixed cation perovskite film prepared using dimethylformamide/dimethylsulfoxide solvent shows greater mobility and diffusion length compared to γ-butyrolactone solvent. Our findings provide valuable insights to improve the charge carrier transport in mixed cation perovskites through solvent engineering. [ABSTRACT FROM AUTHOR]

We aim to find homovalent alternatives for lead and iodine in CH3NH3PbI3 perovskites that show bandgaps suitable for building novel perovskite-perovskite tandem solar cells. To this end, we employ a computational screening for materials with a bandgap between 1.0 eV and 1.9 eV, using density functional theory calculations at the Perdew-Burke-Ernzerhof and Heyd-Scuseria-Ernzerhof levels of theory. The room-temperature stability of the materials and their phases that satisfy the bandgap criteria is evaluated based on the empirical Goldschmidt tolerance factor. In total, our screening procedure covers 30 different perovskite structures in three phases (orthorhombic, cubic, tetragonal) each. We find 9 materials that are predicted to be stable at room temperature and to have bandgaps in an energy range suitable for application in tandem solar cells. [ABSTRACT FROM AUTHOR]

High absorption ability and direct bandgap makes lead-based perovskite to acquire high photovoltaic performance. However, lead content in perovskite becomes a double-blade for counterbalancing photovoltaic performance and sustainability. Herein, we develop a methylammonium bismuth iodide (MBI), a perovskite-derivative, to serve as a lead-free light absorber layer. Owing to the short carrier diffusion length of MBI, its film quality is a predominant factor to photovoltaic performance. Several candidates of non-polar solvent are discussed in aspect of their dipole moment and boiling point to reveal the effects of anti-solvent assisted crystallization. Through anti-solvent engineering of toluene, the morphology, crystallinity, and element distribution of MBI films are improved compared with those without toluene treatment. The improved morphology and crystallinity of MBI films promote photovoltaic performance over 3.2 times compared with the one without toluene treatment. The photovoltaic device can achieve 0.26% with minor hysteresis effect, whose hysteresis index reduces from 0.374 to 0.169. This study guides a feasible path for developing MBI photovoltaics. [ABSTRACT FROM AUTHOR]

In this paper, the influence of post-annealing on the properties of methylammonium bismuth iodide (MBI) perovskite solar cells (PeSCs) fabricated through the hot immersion method (HIM) is reported. The post-annealing temperature varied between 100°C and 250°C. The XRD results showed that the crystallinity of the MBI film was improved, while the surface morphology showed that the flake-shaped structure was enhanced. On increasing the post-annealing temperature, an increase in the average grain size from 0.9 µm to 3 µm was observed. The increase in the grain size led to an enhancement of the optical properties with a narrower indirect bandgap at an extended absorption region towards a longer wavelength. Eventually, the performance of HIM-fabricated MBI PeSCs showed a twofold increase, i.e., from 0.14 V to 0.28 V, for open-circuit voltage, the short-circuit current density of the device increased by more than twofold, and power conversion efficiency increased up to 0.011% with a fivefold increase at 250°C. An improved morphology and enlarged grain size leads to a drastic increase in the efficiency of the devices. Our findings suggest that by using HIM, the performance of MBI solar cells can be improved by post-annealing, providing an alternative, simple method for the fabrication of Pb-free PeSCs in future work. [ABSTRACT FROM AUTHOR]

One effective way of improving the performance of perovskite solar cells (PSCs) is using ionic liquids to control the crystal growth of the perovskite. In this work, the effect of the ionic liquid methylammonium acetate (MAAc) on the perovskite crystal growth and the power conversion efficiency (PCE) of hole-transport material-free PSCs with carbon electrodes were observed. We found that, when perovskite was produced from a reaction of dimethylammonium lead iodide (DMAPbI3) with methylamine, the addition of ionic liquid to the DMAPbI3 precursor solution causes the crystallitic size of the resulting perovskite to increase, improving the crystallinity and light absorbability of the perovskite film. The PCE of the device fabricated by adding 5% MAAc to the DMAPbI3 precursor solution was 14.82%, which was 1.26-fold improved as compared to the control (11.74%). The result of our analysis showed that the PCE of the device was increased by the addition of ionic liquid, due to reduction of the nonradiative recombination and enlargement of the charge recombination resistance. [ABSTRACT FROM AUTHOR]

Three-dimensional hybrid organic–inorganic lead halide perovskites are promising photovoltaic and light-emitting materials. A key phenomenon relevant for their optoelectronic applications is electron–phonon coupling. Since it can be strongly modified by structural deformation and changes in the dynamics of molecular cations, it is of great importance to study the temperature dependence of phonon properties of hybrid perovskites. In this work, temperature-dependent Raman scattering studies of FAPbBr3 and MAPbBr3 single crystals are reported in the 1800–22 cm−1 and 300–90 K ranges. The Raman data of MAPbBr3 showed clear anomalies near 236, 155 and 148 K, which were attributed to Pm3¯m→I4/mcm→P4/mmm (or Imma)→Pnma phase transitions. They also provided strong evidence that crystal structure of the phase stable in the 155–148 K range is very similar to structure of the I4/mcm phase, not structure of the lowest-temperature Pmna phase, as suggested in some reports. Therefore, the symmetry of this phase seems to be more likely P4/mmm rather than Imma. An analysis of the temperature evolution of MAPbBr3 Raman modes revealed that the phase transitions near 236 and 155 K are associated with weak distortion of the inorganic subnetwork and changes in the dynamics of MA+ ions. Very pronounced changes in the lattice modes region and a narrowing of bands below 148 K indicated that the phase transition to the Pnma phase is triggered by a freezing of MA+ motions, which in turn leads to strong distortion of the inorganic subnetwork. Raman studies of FAPbBr3 showed that this material behaves in a very different way than MAPbBr3. First of all, the molecular dynamics of FA+ cations are not frozen even in the lowest-temperature Pnma phase. Moreover, the distortion of the inorganic subnetwork is small in the Pnma phase. The observation of weak anomalies in the lattice modes region confirmed, however, that the two crystallographically resolved phase transitions (Pm3¯m→P4/mbm near 260 K and P4/mbm→Pnma near 150 K) lead to weak distortion of the inorganic subnetwork. On the other hand, an analysis of FA+ internal modes indicated that these transitions, as well as two other crystallographically unresolved transitions near 120 and 180 K, are triggered by a change of FA+ dynamics.