Zn(O,S) film is widely used as a Cd-free buffer layer for kesterite thin film solar cells due to its low-cost and eco-friendly characteristics. However, the low carrier concentration and conductivity of Zn(O,S) will deteriorate the device performance. In this work, an additional buffer layer of In₂S₃ is introduced to modify the properties of the Zn(O,S) layer as well as the CZTSSe layer via a post-annealing treatment. The carrier concentrations of both the Zn(O,S) and CZTSSe layers are increased, which facilitates the carrier separation and increases the open circuit voltage (V_OC). It is also found that ammonia etching treatment can remove the contamination and reduce the interface defects, and there is an increase of the surface roughness of the In₂S₃ layer, which works as an antireflection layer. Consequently, the efficiency of the CZTSSe solar cells is improved by 24% after the annealing and etching treatments. Simulation and experimental results show that a large band offset of the In₂S₃ layer and defect energy levels in the Zn(O,S) layer are the main properties limiting the fill factor and efficiency of these CZTSSe devices. This study affords a new perspective for the carrier concentration enhancement of the absorber and buffer layers by In-doping, and it also indicates that In₂S₃/Zn(O,S) is a promising Cd-free hybrid buffer layer for high-efficiency kesterite solar cells.

Zn（O，S）薄膜由于其低成本和环保特性而被广泛用作钾钛矿薄膜太阳能电池的无Cd缓冲层。但是，Zn（O，S）的低载流子浓度和电导率会降低器件性能。在这项工作中，引入了一个额外的In ₂ S ₃缓冲层，以通过后退火处理来修改Zn（O，S）层以及CZTSSe层的特性。Zn（O，S）和CZTSSe层的载流子浓度均增加，这有助于载流子分离并增加开路电压（V _OC）。还发现，氨蚀刻处理可以去除污染物并减少界面缺陷，并且用作抗反射层的In ₂ S ₃层的表面粗糙度增加。因此，在退火和蚀刻处理之后，CZTSSe太阳能电池的效率提高了24％。仿真和实验结果表明，In ₂ S ₃层的大带隙偏移和Zn（O，S）层中的缺陷能级是限制这些CZTSSe器件的填充因子和效率的主要特性。这项研究为通过In掺杂提高吸收层和缓冲层的载流子浓度提供了新的观点，并且还表明In ₂S ₃ / Zn（O，S）是一种有希望的高效Cesterite太阳能电池无镉混合缓冲层。