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• 作者：Jino Im ; Constantinos C. Stoumpos ; Hosub Jin ; Arthur J. Freeman ; Mercouri G. Kanatzidis
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2015
• 出版时间：September 3, 2015
• 年：2015
• 卷：6
• 期：17
• 页码：3503-3509
• 全文大小：397K
• ISSN：1948-7185

文摘

Halide perovskite solar cells are a recent ground-breaking development achieving power conversion efficiencies exceeding 18%. This has become possible owing to the remarkable properties of the AMX₃ perovskites, which exhibit unique semiconducting properties. The most efficient solar cells utilize the CH₃NH₃PbI₃ perovskite whose band gap, E_g, is 1.55 eV. Even higher efficiencies are anticipated, however, if the band gap of the perovskite can be pushed deeper in the near-infrared region, as in the case of CH₃NH₃SnI₃ (E_g = 1.3 eV). A remarkable way to improve further comes from the CH₃NH₃Sn_1鈥?i>xPb_xI₃ solid solution, which displays an anomalous trend in the evolution of the band gap with the compositions approaching x = 0.5 displaying lower band gaps (E_g 鈮?1.1 eV) than that of the lowest of the end member, CH₃NH₃SnI₃. Here we use first-principles calculations to show that the competition between the spin鈥搊rbit coupling (SOC) and the lattice distortion is responsible for the anomalous behavior of the band gap in CH₃NH₃Sn_1鈥?i>xPb_xI₃. SOC causes a linear reduction as x increases, while the lattice distortion causes a nonlinear increase due to a composition-induced phase transition near x = 0.5. Our results suggest that electronic structure engineering can have a crucial role in optimizing the photovoltaic performance.