Semiconductors such as sulfides have been commonly used as counter electrodes (CEs) in quantum dot sensitized solar cells (QDSCs) with high stability and catalytic activity. But the intrinsic unsatisfactory conductivity has been making researchers find alternative materials for further improving the efficiency. Here nanometer sized copper selenides substrated on F-doped SnO₂ (Cu _x Se/FTO) are used as CE in the construction of QDSCs. Through optimizing the composition and structure variables of the CE materials, including Cu/Se ratio, film thickness, sintering temperature and time, we achieve the power conversion efficiencies up to 6.49% and 8.72% for CdSe and CdSeTe based QDSCs, respectively. Our results show that the excellent photovoltaic performance is strongly associated with the low Cu/Se molar ratio in the range of 1.20–1.38, suggesting the heavily deficient copper in Cu _x Se. The resultant good conductivity and electrochemical catalytic activity of the Cu _x Se/FTO CE have been verified by the electrochemical impedance spectroscopy, Tafel polarization and four-probe measurement results.

中文翻译：

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基于严重缺铜的硒化铜反电极，效率高达8.7％的量子点敏化太阳能电池

诸如硫化物之类的半导体通常已被用作具有高稳定性和催化活性的量子点敏化太阳能电池（QDSC）中的对电极（CE）。但是固有的不令人满意的电导率一直在使研究人员寻找替代材料以进一步提高效率。在此，在掺F的SnO ₂（Cu _xSe / FTO）在QDSC的构造中用作CE。通过优化CE材料的成分和结构变量，包括Cu / Se比，膜厚，烧结温度和时间，我们对基于CdSe和CdSeTe的QDSC的功率转换效率分别达到了6.49％和8.72％。我们的结果表明，优异的光伏性能与1.20–1.38的低Cu / Se摩尔比密切相关，表明Cu _x Se中的铜严重不足。通过电化学阻抗谱，Tafel极化和四探针测量结果验证了Cu _x Se / FTO CE所产生的良好电导率和电化学催化活性。