Gehrmann Christian, Egger David A
Institute of Theoretical Physics, University of Regensburg, 93040, Regensburg, Germany.
Department of Physics, Technical University of Munich, 85748, Garching, Germany.
Nat Commun. 2019 Jul 17;10(1):3141. doi: 10.1038/s41467-019-11087-y.
Halide perovskites are semiconductors that exhibit sharp optical absorption edges and small Urbach energies allowing for efficient collection of sunlight in thin-film photovoltaic devices. However, halide perovskites also exhibit large nuclear anharmonic effects and disorder, which is unusual for efficient optoelectronic materials and difficult to rationalize in view of the small Urbach energies that indicate a low amount of disorder. To address this important issue, the disorder potential induced for electronic states by the nuclear dynamics in various paradigmatic halide perovskites is studied with molecular dynamics and density functional theory. We find that the disorder potential is dynamically shortened due to the nuclear motions in the perovskite, such that it is short-range correlated, which is shown to lead to favorable distributions of band edge energies. This dynamic mechanism allows for sharp optical absorption edges and small Urbach energies, which are highly desired properties of any solar absorber material.
卤化物钙钛矿是一种半导体，具有尖锐的光吸收边缘和较小的乌尔巴赫能量，这使得它们能够在薄膜光伏器件中高效收集太阳光。然而，卤化物钙钛矿也表现出较大的核非谐效应和无序性，这对于高效的光电器件材料来说是不寻常的，并且鉴于表明无序程度较低的小乌尔巴赫能量，很难做出合理的解释。为了解决这个重要问题，我们利用分子动力学和密度泛函理论研究了各种典型卤化物钙钛矿中核动力学对电子态诱导的无序势。我们发现，由于钙钛矿中的核运动，无序势会动态缩短，从而使其具有短程相关性，这被证明会导致带边能量的有利分布。这种动态机制使得卤化物钙钛矿具有尖锐的光吸收边缘和较小的乌尔巴赫能量，而这些正是任何太阳能吸收材料所高度期望的特性。
