锌、黄铜矿和锌黄锡矿太阳能电池材料带边light absorption中的巨振子强度
Giant oscillator strength in the band-edge light absorption of zincblende, chalcopyrite and kesterite solar cell materials
摘要：
在半导体太阳能电池吸收体中，带边区域附近的高吸收系数（α）对于最大化光电流的产生和收集至关重要。然而，尽管带边吸收特性的重要性，带边光学跃迁的定量分析尚未进行。在这项研究中，我们实现了系统的密度泛函理论（DFT）计算，重点是七个实用的太阳能电池吸收剂（GaAs，InP，CdTe，CuInSe 2，CuGaSe 2，Cu2ZnSnSe 4，和Cu2ZnSnS 4）的锌矾，黄铜矿和锌黄铜矿结构的带边振荡强度。我们发现所有这些晶体都在带隙区附近表现出巨振子强度，揭示了带隙区的α被反常的高振子强度显著增强的事实。然而，在高能光跃迁中，振子强度急剧降低，吸收特性主要由联合态密度贡献决定。基于密度泛函理论的结果，我们证明了带边巨振子强度来源于独特的四面体成键结构，而组成原子的影响可以忽略不计。
英文摘要：
In semiconducting solar-cell absorbers, high absorption coefficient (alpha) near the band-edge region is critical to maximize the photocurrent generation and collection. Nevertheless, despite the importance of the band-edge absorption characteristics, the quantitative analysis of the band-edge optical transitions has not been performed. In this study, we have implemented systematic density functional theory (DFT) calculation, focusing on the band-edge oscillator strength of seven practical solar cell absorbers (GaAs, InP, CdTe, CuInSe2, CuGaSe2, Cu2ZnSnSe4, and Cu2ZnSnS4) with zincblende, chalcopyrite and kesterite structures. We find that all these crystals exhibit the giant oscillator strength near the band gap region, revealing the fact that alpha in the band gap region is enhanced significantly by the anomalous high oscillator strength. In high-energy optical transitions, however, the oscillator strength reduces sharply and the absorption properties are determined primarily by the joint density-of-state contribution. Based on DFT results, we show that the giant oscillator strength in the band edge region originates from a unique tetrahedral-bonding structure, with a negligible effect of constituent atoms.
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