Cu(In,Ga)Se₂‐based (CIGS) solar cells with ultrathin (≤500 nm) absorber layers suffer from the low reflectivity of conventional Mo back contacts. Here, we design and investigate ohmic and reflective back contacts (RBC) made of multilayer stacks that are compatible with the direct deposition of CIGS at 500°C and above. Diffusion mechanisms and reactions at each interface and in the CIGS layer are carefully analyzed by energy dispersive X‐ray (EDX)/scanning transmission electron microscopy (STEM). It shows that the highly reflective silver mirror is efficiently encapsulated in ZnO:Al layers. The detrimental reaction between CIGS and the top In₂O₃:Sn (ITO) layer used for ohmic contact can be mitigated by adding a 3 nm thick Al₂O₃ layer and by decreasing the CIGS coevaporation temperature from 550°C to 500°C. It also improves the compositional grading of Ga toward the CIGS back interface, leading to increased open‐ circuit voltage and fill factor. The best ultrathin CIGS solar cell on RBC exhibits an efficiency of 13.5% (+1.0% as compared to our Mo reference) with a short‐circuit current density of 28.9 mA/cm² (+2.6 mA/cm²) enabled by double‐pass absorption in the 510 nm thick CIGS absorber. RBC are easy to fabricate and could benefit other photovoltaic devices that require highly reflective and conductive contacts subject to high temperature processes.

中文翻译：

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反射背触点上超薄Cu（In，Ga）Se2太阳能电池的界面工程

具有超薄（≤500nm）吸收层的基于Cu（In，Ga）Se ₂的（CIGS）太阳能电池具有常规Mo背触点的低反射率的缺点。在这里，我们设计和研究由多层堆叠制成的欧姆和反射背触点（RBC），这些触点与CIGS在500°C及以上的直接沉积兼容。通过能量色散X射线（EDX）/扫描透射电子显微镜（STEM）仔细分析了每个界面以及CIGS层中的扩散机理和反应。它表明高反射银镜被有效地封装在ZnO：Al层中。通过添加3 nm厚的Al ₂ O可以缓解CIGS与用于欧姆接触的顶层In ₂ O ₃：Sn（ITO）层之间的有害反应₃层，并通过将CIGS共蒸发温度从550°C降低到500°C。它还可以改善Ga向CIGS背面界面的成分分级，从而提高开路电压和填充系数。RBC上最好的超薄CIGS太阳能电池表现出13.5％的效率（比Mo基准高+ 1.0％），短路电流密度为28.9 mA / cm ²（+2.6 mA / cm ²），这是由于双在510 nm厚的CIGS吸收器中通过吸收。RBC易于制造，可以使其他需要经过高温处理的高反射和导电触点的光伏器件受益。