In this work, we theoretically investigate spectrum dependent energy harvesting of a thin-film indoor photovoltaic (PV) device, taking into account the role of defects. By numerically solving Poisson’s equation and the continuity equation under optical generation-recombination conditions, performance characteristics of a Cu₂ZnSn(S,Se)₄-based thin-film PV device have been evaluated under spectrally varying white light emitting diodes (LEDs). Without any loss of generality, the results of the experimentally validated theoretical model suggest that a thin-film PV device becomes significantly tolerant to both bulk and interface defects when a fraction of blue emission in the white LED spectra remains relatively low. For a white LED having cool white emission characteristics, the efficiency of a CZTSSe-based PV device can equal the efficiency of the CZTSSe solar cell, the experimentally reported champion, while having about two orders of magnitude higher interface defect density, as well as about twenty times higher bulk defect density. In addition, for all practical densities of both types of defects, the efficiency of the indoor PV device remains at least 20% higher than the efficiency obtained under AM1.5 solar irradiation. The underlying reasons behind such observations have been traced back to the wavelength dependent carrier generation recombination dynamics of the thin-film device stack. The results of this work in effect provide guidelines for designing low-cost yet energy-efficient indoor photovoltaic devices with defect-rich thin film material systems.

中文翻译：

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体缺陷和界面缺陷在基于CZTSSe的室内光伏设备中依赖光谱的能量收集中的作用

在这项工作中，我们从理论上研究了薄膜室内光伏（PV）器件的光谱依赖性能量收集，同时考虑了缺陷的作用。通过光学生成复合条件下的泊松方程和连续性方程数值求解，得出Cu ₂ ZnSn（S，Se）_4的性能特征已经在光谱变化的白光发光二极管（LED）下评估了基于硅的薄膜PV器件。在不失一般性的前提下，经过实验验证的理论模型的结果表明，当白色LED光谱中的一部分蓝色发射保持相对较低时，薄膜PV器件将显着耐受体缺陷和界面缺陷。对于具有冷白光发射特性的白光LED，基于CZTSSe的PV器件的效率可以等于CZTSSe太阳能电池的效率（实验报告的冠军），同时具有较高的界面缺陷密度约两个数量级，以及体积缺陷密度高20倍。此外，对于两种缺陷的所有实际密度，室内光伏设备的效率仍比在AM1.5太阳辐射下获得的效率高出至少20％。此类观察背后的根本原因可追溯到薄膜器件堆叠的与波长相关的载流子产生重组动力学。这项工作的结果实际上为使用缺陷多的薄膜材料系统设计低成本但节能的室内光伏设备提供了指导。