Li Akang, Liu Qi, Chu WeiBin, Liang WanZhen, Prezhdo Oleg V
State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005, People's Republic of China.
Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States.
ACS Appl Mater Interfaces. 2021 Apr 14;13(14):16567-16575. doi: 10.1021/acsami.1c03145. Epub 2021 Apr 1.
Much effort has been dedicated to boost the development of lead-free perovskite solar cells. However, their performance and stability are still much less competitive to the lead-bearing counterparts. By exploiting a mixed Sn-Ge cation strategy for the development of lead-free perovskites, we perform ab initio electronic structure calculations and quantum dynamics simulations on MASnGeI and compare them to MASnI. The calculations demonstrate that the hybrid cation strategy can improve simultaneously the perovskite stability and the lifetime of charge carriers. The stability increases due to a larger space of possible structures within the favorable range of the structural parameters, such as the Goldschmidt tolerance and octahedron factors. By exploring the larger structure space, mixed perovskites find stable configurations with lower free energies and better fitting components that exhibit reduced fluctuations around the equilibrium geometries. Charge carriers live longer in mixed perovskites because cation mixing results in an additional and moderate disorder that separates electrons and holes, reducing their interactions while still maintaining efficient band-like charge transport. These general and fundamental principles established by the analysis of the simulation results are useful for the design of advanced materials for solar energy and construction of optoelectronic devices.
人们已经付出了很多努力来推动无铅钙钛矿太阳能电池的发展。然而，它们的性能和稳定性与含铅同类产品相比仍缺乏竞争力。通过采用混合Sn-Ge阳离子策略来开发无铅钙钛矿，我们对MASnGeI进行了从头算电子结构计算和量子动力学模拟，并将其与MASnI进行比较。计算结果表明，混合阳离子策略可以同时提高钙钛矿的稳定性和电荷载流子的寿命。由于在结构参数（如戈尔德施密特容忍度和八面体因子）的有利范围内可能结构的空间更大，稳定性得以提高。通过探索更大的结构空间，混合钙钛矿找到了具有更低自由能的稳定构型以及更好的拟合组分，这些组分在平衡几何结构周围表现出更小的波动。电荷载流子在混合钙钛矿中的寿命更长，因为阳离子混合会导致额外的适度无序，从而分离电子和空穴，减少它们之间的相互作用，同时仍保持高效的类能带电荷传输。通过对模拟结果的分析所确立的这些普遍而基本的原理，对于太阳能先进材料的设计和光电器件的构建是有用的。
