强关联材料中的光电激发和光伏效应
Optoelectronic excitations and photovoltaic effect in strongly correlated materials
摘要：
基于常规半导体的太阳能电池在将太阳能转换成电方面具有低效率，因为超出入射太阳光子的间隙的多余能量被声子转换成热。在这里，我们通过从头计算方法表明，强相关绝缘体（SCI）中存在强库仑相互作用，导致高度光激发的电子-空穴对通过碰撞电离（II）快速衰减为多个电子-空穴对。我们表明，在绝缘$M_1$阶段的二氧化钒（选择本研究，因为它被认为是一个典型的SCI）的II率是两个数量级高于Si和远高于热电子/空穴衰减率由于声子。我们的研究结果表明，一个相当广泛的类材料可以利用一个有效的太阳能到电能的转换，以前没有考虑过。
英文摘要：
Solar cells based on conventional semiconductors have low efficiency in converting solar energy into electricity because the excess energy beyond the gap of an incident solar photon is converted into heat by phonons. Here we show by ab initio methods that the presence of strong Coulomb interactions in strongly correlated insulators (SCI) causes the highly photo-excited electron-hole pair to decay fast into multiple electron-hole pairs via impact ionization (II). We show that the II rate in the insulating $M_1$ phase of vanadium dioxide (chosen for this study as it is considered a prototypical SCI) is two orders of magnitude higher than in Si and much higher than the rate of hot electron/hole decay due to phonons. Our results indicate that a rather broad class of materials may be harnessed for an efficient solar-to-electrical energy conversion that has been not considered before.
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