无机钙钛矿太阳能电池Cs2SnI6的电子结构和光学性质的第一性原理研究

近年来,Cs2SnI6作为一种无毒性、稳定性好的新型钙钛矿材料应用于太阳能电池中,其电池的光电转换效率由最初不到1%增长到现在的8.5%,使之成为有可能替代铅基钙钛矿太阳能电池的新型太阳能电池。本文采用基于广义密度泛函和杂化密度泛函的第一性原理方法研究了Cs2SnI6的电子结构、光学特性和钙钛矿太阳能电池的光电性能参数。研究结果表明,导带底和价带顶位于同一高对称点Γ而属于直接跃迁型半导体,且电子态主要来自于I-5p轨道和Sn-5s轨道。在近红外和可见光波长范围内有较高的吸收系数,当Cs2SnI6钙钛矿厚度达到10μm时,吸收率在311~989 nm之间接近100%,不考虑潜在损失的情况下,理论上太阳能电池可获得短路电流为32.86 mA/cm2、开路电压0.91 V、填充因子87.4%、光电转换效率26.1%。为实验上制备高效Cs2SnI6钙钛矿太阳能电池提供了参考。

First-principle Study of Electronic and Optical Properties of Inorganic Perovskite Cs2SnI6 for Solar Cells

In recent years,Cs2SnI6 has been used in solar cells as a non-toxic and stable new perovskite material.The power conversion efficiency(PCE)has exceeded 8.5%since the PCE of 1%was first reported in 2014,making the perovskite solar cells the best potential candidate of the new generation solar cells to replace the lead-based perovskite solar cells in the future.The electronic structures and absorption spectra of the defect perovskites Cs2SnI6 were investigated by first-principles calcuation using PBE and HSE06 hybrid functional.The results show that optic band gaps based on HSE06 are 1.023 eV for Cs2SnI6 at theΓ-point,illustrating a direct band gap.Electronic structures calculations show that the conduction band mainly consists of hybridization between the halogen p orbitals and Sn 5s orbitals,whereas the valence band is composed of the halogen p orbitals.The Cs2SnI6 film is adopted as a light absorber layer for a lead-free perovskite solar cell and the power conversion efficiency 26.1%with open-circuit voltage of 0.91 V and short-circuit current of 32.86 mA/cm2 is realized by optimizing the perovskite absorber thickness of 10μm.It provides a reference for the experimental preparation of high-efficiency Cs2SnI6 perovskite solar cells.