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Toxic elements such as lead, instability, and low efficiency are some of the challenges of producing organic-inorganic solar cells. In this research, methylammonium Sn-based halide perovskite (MASnI 3) with less toxicity and a normal structure was modeled. The simulated cell configuration consisted of FTO / PC 61 BM / MASnI 3 / PEDOT : PSS + WO 3 / Cu layers. In this research, water-free poly(3,4-ethylenedioxythiophene): poly styrene sulfonate (PEDOT: PSS) and tungsten trioxide (WO 3) nanoparticles were used as the hole‐transport layer (HTL) and phenyl- C 61 -butyric acid methyl ester (PC 61 BM) as the electron-transport layer (ETL). This research investigated the effects of variation in the device parameters of some layers on the performance parameters and determined the optimal value for each layer to improve power conversion efficiency (PCE). In another structure, the absorber layer was replaced with formamidinium tin iodide-based perovskite (FASnI 3), and after finding the optimal values for the device parameters, the results were compared with the previous structure. The comparison results indicated that the structure with FASnI 3 outperforms MASnI 3. The simulations were conducted in the SCAPS-1D environment. The optimal results obtained from the structure with FASnI 3 -based perovskite after optimizations were as follows: short-circuit current density (J SC) of 24.65 mA / cm 2 , open-circuit voltage (V OC) of 1.12 V, fill factor (%FF) of 86.02%, and PCE of 23.69%. • A water-free PEDOT was studied. • The effect of increasing the doping concentration was investigated. • Effects of the absorber layer with formamidinium-based perovskite (FASnI 3), was investigated. • High performance solar cell was obtained by optimization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrasonication synthesis of lead deficient MAPb1 -x Zn x Br 3 PQDs. • High PLQY > 93% for Zn doped MAPbBr 3 in open atmosphere. • Variation of Zn concentration in MAPbBr 3 for the first time. • Incorporation of Zn2+ ions improves the stability. • Demonstration of warm white LED prototype with 124% color gamut. B-site substitution perovskite quantum dots (PQDs) with amended stability and less toxicity have been acquainted in recent years. However, the PQDs comprising various B-site cations display low photoluminescence quantum yields (PLQYs), instability, and require skimpy synthesis procedure. Herein, we have endeavored to introduce ultrasonication synthesis of MAPb1 -x Zn x Br 3 PQDs as an auspicious route to stable PQDs with enhanced PLQY. The successful synthesis of PQDs resulted in a high PLQY (>93%), which is supposed to be owing to the decrease in non-radiative recombination centers. Furthermore, we have found that the structure, morphology, and emission properties are secured with the substitution of Zn2+. The PQDs have been integrated as color converting layers coated on blue light emitting diode (LED) chips, which exhibit white light with the wide color gamut of National Television Standards Committee (NTSC) 124%. The present research reveals a new synthesis route to obtain stable and efficient PQDs without negotiating color quality for display application. [ABSTRACT FROM AUTHOR]

• Schematic drawing of the CH3NH3PbI3-xClx/GaN microwire array heterostructures photodetector. • Characterization of the CH3NH3PbI3-xClx/GaN microwire array photodetector. • Photoelectric performance compared to the hybrid three types of photodetectors from ultraviolet to visible light region. • I-V curves with or without perovskite layer measured in the dark and under 325 nm light irradiation. • The mechanism to improve the performance of heterostructure photodetector was discussed In recent years, the combination of perovskites with other materials to improve the photoelectric performance has received widespread attention. In this work, we demonstrate a hybrid heterostructure photodetector with the combination of GaN microwire array and perovskite. Compared to perovskite and GaN microwire array photodetectors, the hybrid CH 3 NH 3 PbI 3- x Cl x /GaN microwire array photodetector exhibits more excellent photoelectric performances in a wide detection range from ultraviolet to visible. Under 325 nm laser irradiation, the hybrid photodetector generates a large photocurrent (1.04 ×10-5 A), a high on/off ratio (>104), a fast response time (raise time of 0.66 ms and decay time of 0.71 ms), and higher responsivity , detectivity. Meanwhile, when the perovskite is combined with the GaN microwire array, the device also has a higher photocurrent, on/off ratio, and faster photoresponse compared with the perovskite photodetector in the visible light region. This is interpreted as the effective separation photogenerated carriers at the hetero-interface, and the directional transfer of carriers within the one-dimensional GaN microwire array. This study sheds light on fabricating high-performance heterostructures photodetectors. [ABSTRACT FROM AUTHOR]

Herein, we reported the introduction of carbon nanodots (CNDs) and polyvinylidene fluoride (PVDF) as additives into perovskite CH 3 NH 3 PbI 3 through in situ synthesis to prepare PVDF-CH 3 NH 3 PbI 3 @CNDs composite, which demonstrated improved water tolerance and mechanical stability. The application of PVDF-CH 3 NH 3 PbI 3 @CNDs for photoelectrochemical sensing was then explored. A molecularly imprinted polymer (MIP) that could specifically recognize cholesterol (CHO) was anchored to PVDF-CH 3 NH 3 PbI 3 @CNDs via a simple thermal polymerization process, followed by elution with hexane. A label-free and sensitive photoelectrochemical method for CHO detection was achieved by using the MIPs@PVDF-CH 3 NH 3 PbI 3 @CNDs platform. The detection limit for CHO was 2.1 × 10−14 mol/L, lower than most of the existing CHO detection methods. In our perception, this platform can be extended to numerous other analytes. This research result may provide a new understanding to improve the performance and broaden the application range of organic-inorganic perovskites. Image 1 • Carbon nanodots and molecular imprinted polymers (MIPs) were both used to functionalize CH 3 NH 3 PbI 3. • The functionalized CH 3 NH 3 PbI 3 showed good aqueous stability and selectivity. • A novel PEC sensor for cholesterol was constructed based on the functionalized perovskites. [ABSTRACT FROM AUTHOR]

• Humidity is intensively impact the instability of hybrid organic-inorganic perovskites. • For unpacked device, symmetric hysteresis loop rotation converts from anticlockwise to clockwise. • For one-end packed device, hysteresis loops transform from anticlockwise symmetry to antisymmetry. • Modulable hysteresis is from the decrease of surface state and the formation of PbI2 and bulk defect. • Electrical field-triggered filling and emptying of traps dominate adjustable electric transport. The instability of hybrid organic-inorganic perovskites (HOIP) in environment, especially in high humidity causes different conductance that should be addressed to improve its large-scale application and development. Here, the electrical transport of an individual CH 3 NH 3 PbI 3 micro/nanowire-based two-terminal device with encapsulating different ends was investigated in a condensed water environment. For an unencapsulated device, linear I-V curve transforms first into two symmetrical counterclockwise hysteresis loops with positive resistive switching (RS) feature, and eventually converts into two symmetrical clockwise hysteresis loops with negative RS feature. For the device encapsulated at one end, the linear I-V curve first transforms into two symmetrical counterclockwise hysteresis loops with positive RS behavior, and then converts into two antisymmetric hysteresis loops with a bipolar RS feature. The origin of modulable hysteresis with different RS characteristics is mainly from the decomposition-induced decrease of surface states and formation of PbI 2 and structure defects. As a consequence, the electrical field-triggered filling and emptying of traps in different regions dominate the adjustable performance of electrical transport. The controllable electrical transport can not only demonstrate clearly that condensed water can promote the decomposition of CH 3 NH 3 PbI 3 , but also verify that the hysteresis behavior with different RS memory effect originate from the decomposition-induced traps. [ABSTRACT FROM AUTHOR]

The current work presents structural change and band gap tunability using hybrid organic-inorganic perovskite with the incorporation of long chain ammonium halide. Thin films of MAPbI 3 with different ratio of n-butylammonium iodide (BAI) have been successfully deposited on the substrate using a single step coating technique. X-ray diffraction scans revealed the transition of the 3D structure of MAPbI 3 to quasi-2D perovskite structure when BAI loading increase with a crystallite size range approximately 16 nm. This structural changeis reflected in the band gap as it increased from 1.59 eV for bulk crystal MAPbI 3 to 2.13 eV for BAI and MAPbI 3 ratio of 1:1. Correspondingly, photoluminescence measurement showed a blue shift in perovskite emission due to the transition of 3D to 2D layered structure perovskite. Raman spectra confirm that all fabricated films are of pristine quality and no corresponding degradation peaks of PbI 2 is observed. These characteristics are important to address the single step deposition method of hybrid perovskite for perovskite solar cells application., (© 2020 Published by Elsevier Ltd.)

Lead‐free and organic–inorganic hybrid (CH3NH3)2CoCl4 [(MA)2CoCl4] single crystal and thin film are prepared. The single crystal diffraction data of (MA)2CoCl4 are assigned to monoclinic, P2(1)/C space group (7.6590 × 12.6908 × 10.89350 Å, 90.0 × 96.5320 × 90.000). The absorption edge of (MA)2CoCl4 reaches 730 nm. The band gap for (MA)2CoCl4 is determined to be approximately 1.63 eV. To the best of our knowledge, this is the first study on (MA)2CoCl4 for optoelectronic applications. A low‐cost photodetector based on (MA)2CoCl4 thin film is efficient under different monochromatic light from 330 nm to 400 nm with different chopping frequencies (1.33–60 Hz). The strongest photoresponse (Ion − Ioff) is under 330 nm monochromatic light with 1.33 Hz according to our optimal condition. The calculational results by density functional theory show that the narrow valence bands and conduction bands are derived from the 3p orbitals of Cl and 3d orbitals of Co. A low‐cost photodetector based on (MA)2CoCl4 thin film is efficient under different monochromatic light from 330 nm to 400 nm with different chopping frequencies (1.33–60 Hz). The calculational results by density functional theory show that the narrow valence bands and conduction bands are derived from the 3p orbitals of Cl and 3d orbitals of Co. [ABSTRACT FROM AUTHOR]

Lead‐free and organic–inorganic hybrid (CH3NH3)2CoCl4 [(MA)2CoCl4] single crystal and thin film are prepared. The single crystal diffraction data of (MA)2CoCl4 are assigned to monoclinic, P2(1)/C space group (7.6590 × 12.6908 × 10.89350 Å, 90.0 × 96.5320 × 90.000). The absorption edge of (MA)2CoCl4 reaches 730 nm. The band gap for (MA)2CoCl4 is determined to be approximately 1.63 eV. To the best of our knowledge, this is the first study on (MA)2CoCl4 for optoelectronic applications. A low‐cost photodetector based on (MA)2CoCl4 thin film is efficient under different monochromatic light from 330 nm to 400 nm with different chopping frequencies (1.33–60 Hz). The strongest photoresponse (Ion − Ioff) is under 330 nm monochromatic light with 1.33 Hz according to our optimal condition. The calculational results by density functional theory show that the narrow valence bands and conduction bands are derived from the 3p orbitals of Cl and 3d orbitals of Co. A low‐cost photodetector based on (MA)2CoCl4 thin film is efficient under different monochromatic light from 330 nm to 400 nm with different chopping frequencies (1.33–60 Hz). The calculational results by density functional theory show that the narrow valence bands and conduction bands are derived from the 3p orbitals of Cl and 3d orbitals of Co. [ABSTRACT FROM AUTHOR]

Lead halide perovskites are used in thin-film solar cells, which owe their high efficiency to the long lifetimes of photocarriers. Various calculations find that a dynamical Rashba effect could significantly contribute to these long lifetimes. This effect is predicted to cause a spin splitting of the electronic bands of inversion-symmetric crystalline materials at finite temperatures, resulting in a slightly indirect band gap. Direct experimental evidence of the existence or the strength of the spin splitting is lacking. Here, we resonantly excite photocurrents in single crystalline ([Formula: see text])[Formula: see text] with circularly polarized light to clarify the existence of spin splittings in the band structure. We observe a circular photogalvanic effect, i.e., the photocurrent depends on the light helicity, in both orthorhombic and tetragonal ([Formula: see text])[Formula: see text] At room temperature, the effect peaks for excitation photon energies [Formula: see text] meV below the direct optical band gap. Temperature-dependent measurements reveal a sign change of the effect at the orthorhombic-tetragonal phase transition, indicating different microscopic origins in the two phases. Within the tetragonal phase, both [Formula: see text] and the amplitude of the circular photogalvanic effect increase with temperature. Our findings support a dynamical Rashba effect in this phase, i.e., a spin splitting caused by thermally induced structural fluctuations which break inversion symmetry.

Precisely controlling the optimal amount of hydration water in the precursor solution, results in the formation of a smooth and uniform perovskite film, as described by Y. Zhan, L. Zheng, and co‐workers on page 5028. With appropriate annealing, the perovskite monohydrate loses its hydration water and crystallizes into pristine MAPbI3. The simplicity of controlling hydration water during precursor solution preparation will influence mass production of perovskite solar cells. [ABSTRACT FROM AUTHOR]

A simple yet general swelling-deswelling microencapsulation strategy has been developed to achieve well dispersed and intimately passivated crystalline organic-inorganic perovskites nanoparticles within polymer matrixes and results in a series of highly luminescent CH 3 NH 3 PbBr 3 (MAPbBr 3 )-polymer composite films with unprecedented water and thermal stabilities and superior color purity., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A challenge of hybrid perovskite solar cells is device instability, which calls for an understanding of the perovskite structural stability and phase transitions. Using neutron diffraction and first-principles calculations on formamidinium lead iodide (FAPbI 3 ), we show that the entropy contribution to the Gibbs free energy caused by isotropic rotations of the FA + cation plays a crucial role in the cubic-to-hexagonal structural phase transition. Furthermore, we observe that the cubic-to-hexagonal phase transition exhibits a large thermal hysteresis. Our first-principles calculations confirm the existence of a potential barrier between the cubic and hexagonal structures, which provides an explanation for the observed thermal hysteresis. By exploiting the potential barrier, we demonstrate kinetic trapping of the cubic phase, desirable for solar cells, even at 8.2 K by thermal quenching.