FA0.8MA0.2SnxPb1–xI3 Hybrid Perovskite Solid Solution: Toward Environmentally Friendly, Stable, and Near-IR Absorbing Materials

Centimeter-Size Single Crystals of Halide Perovskite Photoferroelectric Solid Solution with Ultrahigh Pyroelectricity Boosted Photodetection

Photoferroelectrics, especially emerging halide perovskite ferroelectrics, have motivated tremendous interests owing to their fascinating bulk photovoltaic effect (BPVE) and cross-coupled functionalities. However, solid solutions of halide perovskite photoferroelectrics with controllable structure and enhanced performance are scarcely explored. Herein, through mixing cage cation, a homogeneous halide perovskite photoferroelectric PA2 FAx MA1-x Pb2 Br7 solid solution (PA, FA and MA are CH3 CH2 CH2 NH3 + , NH2 CHNH2 + and CH3 NH3 + , 0≤x≤1) has been developed, which demonstrates tunable Curie temperature in a wide range of 263-323 K and excellent optoelectrical features. As the component adjusted to x=0.7, the bulk crystal demonstrates ultrahigh pyroelectric coefficient up to 1.48 μC cm-2  K-1 around room temperature. Strikingly, benefiting from the light-induced pyroelectricity and remarkable BPVE, a self-powered and sensitive photodetector based solid solution crystals with boosted responsivity and detectivity over than 1300 % has been achieved. This pioneering work sheds light on the exploration of photoferroelectric solid solutions towards high-performance photoelectronic devices.

Doping-Induced Rapid Decoherence Suppresses Charge Recombination in Mono/Divalent Cation Mixed Perovskites from Nonadiabatic Molecular Dynamics Simulation

Experiment shows that solar cells based on FA_0.75Cs_0.25Pb_0.5Sn_0.5I₃ carry a lower charge recombination rate and higher power conversion efficiency than those of FAPbI₃ despite the fact that the former has a smaller band gap. However, the underlying mechanism remains unclear. Using nonadiabatic (NA) molecular dynamics, we demonstrate that low-frequency vibrations drive electron-hole recombination in pristine FAPbI₃ occurring in about 1 ns, showing excellent agreement with experiment. Cs/Sn substitution to FA/Pb not only narrows its band gap by 0.3 eV but also delocalizes the electron wave function significantly, leading to enhancement of NA coupling. Importantly, doping accelerates quantum decoherence caused by increased atomic fluctuations. As a result, rapid decoherence prevails a small band gap and strong NA coupling, slowing charge recombination and extending the charge carriers' lifetime to several nanoseconds. Our study reveals the importance of quantum coherence on quantum dynamics in perovskite materials and suggests a rational strategy to design high-performance perovskite solar cells.

Realizing Full Coverage of Stable Perovskite Film by Modified Anti-Solvent Process

Lead-free solution-processed solid-state photovoltaic devices based on formamidinium tin triiodide (FASnI₃) and cesium tin triiodide (CsSnI₃) perovskite semiconductor as the light harvester are reported. In this letter, we used solvent engineering and anti-solvent dripping method to fabricate perovskite films. SnCl₂ was used as an inhibitor of Sn⁴⁺ in FASnI₃ precursor solution. We obtained the best films under the function of toluene or chlorobenzene in anti-solvent dripping method and monitored the oxidation of FASnI₃ films in air. We chose SnF₂ as an additive of CsSnI₃ precursor solution to prevent the oxidation of the Sn²⁺, improving the stability of CsSnI₃. The experimental results we obtained can pave the way for lead-free tin-based perovskite solar cells (PSCs).