Antagonism between Spin-Orbit Coupling and Steric Effects Causes Anomalous Band Gap Evolution in the Perovskite Photovoltaic Materials CH3NH3Sn1-xPbxI3
Antagonism between Spin-Orbit Coupling and Steric Effects Causes Anomalous Band Gap Evolution in the Perovskite Photovoltaic Materials CH3NH3Sn1-xPbxI3
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DOI：
10.1021/acs.jpclett.5b01738
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发表时间：
2015-09-03
影响因子：
5.7
通讯作者：
Kanatzidis, Mercouri G.
中科院分区：
文献类型：
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作者：
Im, Jino;Stoumpos, Constantinos C.;Kanatzidis, Mercouri G.
卤化物钙钛矿太阳能电池是最近的突破性发展，其功率转换效率超过18%。由于AMX（3）钙钛矿的显着特性，这已经成为可能，其表现出独特的半导体特性。最有效的太阳能电池利用CH 3 NH3 PbI 3钙钛矿，其带隙Eg为1.55 eV。然而，如果钙钛矿的带隙可以在近红外区域中被推得更深，则可以预期甚至更高的效率，如在CH 3 NH3 SnI 3（Eg = 1.3eV）的情况下。进一步改进的显著方式来自CH 3 NH3 Sn 1 PbI 3固溶体，其在带隙的演变中显示出异常趋势，其中组成接近x = 0.5，显示出比最低端元CH 3 NH3 SnI 3的带隙更低的带隙（E-g接近1.1eV）。在这里，我们使用第一性原理计算表明，自旋轨道耦合（SOC）和晶格畸变之间的竞争是负责的带隙在CH 3 NH3 Sn 1-xPbI 3的异常行为。SOC引起的线性减少，随着x的增加，而晶格畸变引起的非线性增加，由于组成诱导的相变接近x = 0.5。我们的研究结果表明，电子结构工程可以在优化光伏性能的关键作用。
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 AMX(3) perovskites, which exhibit unique semiconducting properties. The most efficient solar cells utilize the CH3NH3PbI3 perovskite whose band gap, Eg, 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 (Eg = 1.3 eV). A remarkable way to improve further comes from the CH3NH3Sn,,PbI3 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 approximate to 1.1 eV) than that of the lowest of the end member, CH3NH3SnI3. Here we use firstprinciples calculations to show that the competition between the spin orbit coupling (SOC) and the lattice distortion is responsible for the anomalous behavior of the band gap in CH3NH3Sn1-xPbI3. 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.