Kalita Dhiman, Nandi Pronoy, Sahu Puspanjali, Schoekel Alexander, van Embden Joel, Topwal Dinesh, Manju Unnikrishnan
Materials Chemistry Department, CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751013, India.
Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India.
J Phys Chem Lett. 2024 Mar 7;15(9):2557-2565. doi: 10.1021/acs.jpclett.4c00250. Epub 2024 Feb 28.
The optoelectronic properties of organic lead halide perovskites (OLHPs) strongly depend on their underlying crystal symmetry and dynamics. Here, we exploit temperature-dependent synchrotron powder X-ray diffraction and temperature-dependent photoluminescence to investigate how the subtle structural changes happening in the pure and mixed A-site cation MAFAPbBr ( = 0, 0.5, and 1) systems influences their optoelectronic properties. Diffraction investigations reveal a cubic structure at high temperatures and tetragonal and orthorhombic structures with octahedral distortion at low temperatures. Steady state photoluminescence and time correlated single photon counting study reveals that the dual emission behavior of these OLHPs is due to the direct-indirect band formation. In the orthorhombic phase of MAPbBr, the indirect band is dominated by self-trapped exciton (STE) emission due to the higher-order lattice distortions of PbBr octahedra. Our findings provide a comprehensive explanation of the dual emission behavior of OLHPs while also providing a rationale for previous experimental observations.
有机卤化铅钙钛矿（OLHPs）的光电特性强烈依赖于其潜在的晶体对称性和动力学。在此，我们利用温度依赖的同步辐射粉末X射线衍射和温度依赖的光致发光来研究在纯的和混合的A位阳离子MAFAPbBr（x = 0、0.5和1）体系中发生的细微结构变化如何影响其光电特性。衍射研究表明，在高温下为立方结构，在低温下为具有八面体畸变的四方和正交结构。稳态光致发光和时间相关单光子计数研究表明，这些OLHPs的双发射行为是由于直接-间接能带形成。在MAPbBr的正交相中，由于PbBr八面体的高阶晶格畸变，间接带由自陷激子（STE）发射主导。我们的研究结果对OLHPs的双发射行为提供了全面解释，同时也为先前的实验观察提供了理论依据。
