Kumar Manish, Singh Arunima, Gill Deepika, Bhattacharya Saswata
Department of Physics, Indian Institute of Technology Delhi, New Delhi, India.
J Phys Chem Lett. 2021 Jun 10;12(22):5301-5307. doi: 10.1021/acs.jpclett.1c01034. Epub 2021 Jun 1.
Chalcogenide perovskites have emerged as lead-free, stable photovoltaic materials, having promising optoelectronic properties. However, a detailed theoretical study on excitonic properties is rather demanding task due to the huge computational cost and, therefore, is hitherto unknown. Here, we report the excitonic properties of chalcogenide perovskites AZrS (A = Ca, Sr, Ba) using state-of-the-art hybrid density functional theory and many-body perturbation theory (within the framework of GW and BSE). We find the exciton binding energy () is larger than that of conventional halide perovskites. We also observe, by computing the electron-phonon coupling parameters, a more stable charge-separated polaronic state as compared to that of the bound exciton. The ionic contribution to dielectric screening is found to be negligible in this class of materials. On the basis of the direct band gap and the absorption coefficient, the estimated spectroscopic limited maximum efficiency is quite good when these materials are considered as promising environmentally friendly perovskites suitable for photovoltaics.
硫族钙钛矿已成为无铅、稳定的光伏材料，具有良好的光电性能。然而，由于巨大的计算成本，对其激子特性进行详细的理论研究是一项相当艰巨的任务，因此迄今为止尚不清楚。在这里，我们使用最先进的杂化密度泛函理论和多体微扰理论（在GW和BSE框架内）报告硫族钙钛矿AZrS（A = Ca、Sr、Ba）的激子特性。我们发现激子结合能（）大于传统卤化物钙钛矿。通过计算电子-声子耦合参数，我们还观察到与束缚激子相比，电荷分离的极化子态更稳定。在这类材料中，离子对介电屏蔽的贡献可忽略不计。基于直接带隙和吸收系数，当这些材料被视为适用于光伏的有前景的环保钙钛矿时，估计的光谱极限最大效率相当不错。
