Chang Junli, Jiang Liping, Wang Guangzhao, Zhao Wei, Huang Yuhong, Chen Hong
School of Physical Science and Technology, Southwest University, Chongqing 400715, People's Republic of China.
Key Laboratory of Extraordinary Bond Engineering and Advanced Materials Technology of Chongqing, School of Electronic Information Engineering, Yangtze Normal University, Chongqing 408100, People's Republic of China.
Phys Chem Chem Phys. 2021 Jul 7;23(26):14449-14456. doi: 10.1039/d1cp00024a.
Hybrid perovskites are favoured over other numerous optoelectronic materials, thanks to their rapidly enhanced power conversion efficiency (PCE) and facile processing. At present, future developments are seriously hampered by the high toxicity of heavy metals and poor stability. Inorganic lead-free perovskites, CsSn1-xGexI3-yBry, are herein explored for superior optical performance by first-principles calculations based on density functional theory (DFT). It is unveiled that the valence band maximum (VBM) is mainly occupied by the p-orbit of halide ions, while the conduction band minimum (CBM) is composed of the p-orbit of the metal ion. Moreover, Bader charge analysis shows that CsSn0.5Ge0.5I3 corresponds to the most obvious charge transfer compared to the others. The defect formation energy indicates that perovskite compounds CsSn1-xGexI3-yBry, are more easily synthesized than the series CsSn1-xGexI3, and the physically accessible area is also determined in the coordinate system defined by the chemical potential change of the host atoms, ΔμSn and ΔμI. Additionally, the absorption spectra show that among the doped compounds of the form CsSn0.5Ge0.5I3-yBry, perovskite CsSn0.5Ge0.5I2Br is superior in terms of optical response in the visible-light range. The results shed a new light on the study of highly efficient and stable lead-free perovskite-based solar cells (PSCs).
混合钙钛矿因功率转换效率（PCE）迅速提高且易于加工，而优于其他众多光电子材料。目前，重金属的高毒性和稳定性差严重阻碍了其未来发展。本文基于密度泛函理论（DFT）通过第一性原理计算探索无机无铅钙钛矿CsSn1-xGexI3-yBry的优异光学性能。结果表明，价带最大值（VBM）主要由卤离子的p轨道占据，而导带最小值（CBM）由金属离子的p轨道组成。此外，巴德电荷分析表明，与其他物质相比，CsSn0.5Ge0.5I3的电荷转移最为明显。缺陷形成能表明，钙钛矿化合物CsSn1-xGexI3-yBry比CsSn1-xGexI3系列更容易合成，并且在由主体原子的化学势变化ΔμSn和ΔμI定义的坐标系中也确定了物理可达区域。此外，吸收光谱表明，在CsSn0.5Ge0.5I3-yBry形式的掺杂化合物中，钙钛矿CsSn0.5Ge0.5I2Br在可见光范围内的光学响应方面表现优异。这些结果为高效稳定的无铅钙钛矿基太阳能电池（PSC）的研究提供了新的思路。
