论文标题
激子及其在原子GW/BSE计算中的卤化卤化物钙钛矿纳米晶体中的精细结构
Excitons and their Fine Structure in Lead Halide Perovskite Nanocrystals from Atomistic GW/BSE Calculations
论文作者
论文摘要
纳米晶体的原子详细计算研究，例如源自有希望的六角甲基钙钛矿的纳米晶体，由于原子数量和缺乏对称性的利用而挑战。在这里，着眼于碘化碘化物纳米晶体，我们将真实空间的紧密结合模型与GW近似与自能力的近似结合在一起，并通过相关的Bethe-Salpeter方程的溶液获得激子波函数和吸收光谱。我们发现，载体限制，介电对比度，电子孔交换和激子结合能的尺寸依赖性对最低激发能的影响很大，在2-6 nm的直径范围内，该兴奋能可以调节几乎1 eV。我们计算出的激发能比实验测量的光致发光高约0.2 eV，它们显示出相同的质量依赖性。着眼于带边缘激子的精细结构，我们发现最低的激子在光谱上是黑暗的，能量比较高的明亮状态的三胞胎低约20-30 mev，其脱位因晶体场效应而略微破裂。
Atomistically detailed computational studies of nanocrystals, such as those derived from the promising lead-halide perovskites, are challenging due to the large number of atoms and lack of symmetries to exploit. Here, focusing on methylammonium lead iodide nanocrystals, we combine a real-space tight binding model with the GW approximation to the self-energy and obtain exciton wavefunctions and absorption spectra via solutions of the associated Bethe-Salpeter equation. We find that the size dependence of carrier confinement, dielectric contrast, electron-hole exchange, and exciton binding energies has a strong impact on the lowest excitation energy, which can be tuned by almost 1 eV over the diameter range of 2-6 nm. Our calculated excitation energies are about 0.2 eV higher than experimentally measured photoluminescence, and they display the same qualitative size dependence. Focusing on the fine structure of the band-edge excitons, we find that the lowest-lying exciton is spectroscopically dark and about 20-30 meV lower in energy than the higher-lying triplet of bright states, whose degeneracy is slightly broken by crystal field effects.
