Role of Polar Phonons in the Photo Excited State of Metal Halide Perovskites.
Role of Polar Phonons in the Photo Excited State of Metal Halide Perovskites.
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DOI：
10.1038/srep28618
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发表时间：
2016-06-28
影响因子：
4.6
通讯作者：
Kresse G
中科院分区：
文献类型：
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作者：
Bokdam M;Sander T;Stroppa A;Picozzi S;Sarma DD;Franchini C;Kresse G
高效钙钛矿太阳能电池的发展引发了对这些材料光学特性的大量测量。对于研究最多的甲基铵（MA）PbI 3钙钛矿，各种实验已经报道了大范围（6-55 meV）的激子结合能。激子在室温下是否存在还不清楚。对于MAPbX 3钙钛矿，我们报告相对论Bethe-Salpeter方程计算（GW-BSE）。该方法能够直接从第一性原理计算激子性质。在低温下，它预测激子结合能与报告的“大”值。对于MAPbI 3，声子模式存在于这个频率范围内的离子屏蔽的贡献可以忽略不计。通过从有限温度分子动力学计算极化的时间，我们表明，在室温下，这不会改变。因此，我们排除离子屏蔽作为实验观察到的激子结合能在室温下减少的解释，并主张有利于形成极化子。
The development of high efficiency perovskite solar cells has sparked a multitude of measurements on the optical properties of these materials. For the most studied methylammonium(MA)PbI3 perovskite, a large range (6–55 meV) of exciton binding energies has been reported by various experiments. The existence of excitons at room temperature is unclear. For the MAPbX3 perovskites we report on relativistic Bethe-Salpeter Equation calculations (GW-BSE). This method is capable to directly calculate excitonic properties from first-principles. At low temperatures it predicts exciton binding energies in agreement with the reported ‘large’ values. For MAPbI3, phonon modes present in this frequency range have a negligible contribution to the ionic screening. By calculating the polarization in time from finite temperature molecular dynamics, we show that at room temperature this does not change. We therefore exclude ionic screening as an explanation for the experimentally observed reduction of the exciton binding energy at room temperature and argue in favor of the formation of polarons.