The earth-abundant material CuSbS₂ (CAS) has shown good optical properties as a photovoltaic solar absorber material, but has seen relatively poor solar cell performance. To investigate the reason for this anomaly, the core levels of the constituent elements, surface contaminants, ionization potential, and valence-band spectra are studied by X-ray photoemission spectroscopy. The ionization potential and electron affinity for this material (4.98 and 3.43 eV) are lower than those for other common absorbers, including CuIn_xGa_(1–x)Se₂ (CIGS). Experimentally corroborated density functional theory (DFT) calculations show that the valence band maximum is raised by the lone pair electrons from the antimony cations contributing additional states when compared with indium or gallium cations in CIGS. The resulting conduction band misalignment with CdS is a reason for the poor performance of cells incorporating a CAS/CdS heterojunction, supporting the idea that using a cell design analogous to CIGS is unhelpful. These findings underline the critical importance of considering the electronic structure when selecting cell architectures that optimize open-circuit voltages and cell efficiencies.

中文翻译：

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用于太阳能电池的CuSbS _2的核心能级，能带对准和价带态

富含地球的材料CuSbS ₂（CAS）作为光伏太阳能吸收材料具有良好的光学性能，但太阳能电池的性能却相对较差。为了研究这种异常的原因，通过X射线光电子能谱研究了组成元素的核心能级，表面污染物，电离势和价带谱。该材料的电离势和电子亲和力（4.98和3.43 eV）低于其他常见吸收剂，包括CuIn _x Ga _{（1– x）} Se ₂（CIGS）。实验证实的密度泛函理论（DFT）计算表明，与CIGS中的铟或镓阳离子相比，锑阳离子的孤对电子提高了价带的最大值，从而贡献了附加态。导致的CdS导带失准是引入CAS / CdS异质结的电池性能不佳的原因，这支持了使用类似于CIGS的电池设计无济于事的想法。这些发现强调了在选择优化开路电压和电池效率的电池架构时考虑电子结构的至关重要性。