Graphic-carbon nitride (g-C3N4) microsheet loaded with CuS nanocrystals was coated on fluorine-doped tin oxide (FTO) conductive glass to act as counter electrodes (CEs) in quantum dots sensitized solar cells (QDSCs) for the first time. The successive ionic layer absorption and reaction (SILAR) method was employed to fabricate CuS nanocrystals in different amounts onto the surface of g-C3N4 microsheets through varying deposition cycle times (0, 1, 3, 5, and 7). From the results of SEM and TEM, it was found that the amount of CuS nanocrystals deposited on the surface of g-C3N4 increased gradually with the CuS deposition cycle times. According to the results of the electrical impedance spectrum, series resistance and charge transfer impedance exhibited a declining trend until CuS deposition cycle time was up to 5, which was proved through Tafel curves as well. According to current density–voltage curve results of all these cell samples, g-C3N4 with five cycle times QDSC yielded the highest power conversion efficiency and corresponding charge transfer resistance was the lowest, while the cell based on CuS/g-C3N4 CE of seven cycle times presented worse photovoltaic performance due to the aggregation of excessive CuS particles. The optimized CuS/g-C3N4 CEs possessed the fast electron transfer and superior electrocatalytic ability, which are critical in high-performance QDSCs.

中文翻译：

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CuS/gC$_{3}$N$_{4}$ 复合材料作为 QDSC 中的高性能对电极材料

载有 CuS 纳米晶体的图形氮化碳 (g-C3N4) 微片被涂覆在掺氟氧化锡 (FTO) 导电玻璃上，首次用作量子点敏化太阳能电池 (QDSC) 中的对电极 (CE)。采用连续离子层吸收和反应 (SILAR) 方法，通过不同的沉积循环时间（0、1、3、5 和 7）在 g-C3N4 微片表面上制备不同数量的 CuS 纳米晶体。从SEM和TEM结果可以发现，随着CuS沉积循环次数的增加，沉积在g-C3N4表面的CuS纳米晶的数量逐渐增加。根据电阻抗谱结果，串联电阻和电荷转移阻抗呈下降趋势，直至 CuS 沉积循环时间达到 5，塔菲尔曲线也证明了这一点。根据所有这些电池样品的电流密度-电压曲线结果，具有五个循环次数 QDSC 的 g-C3N4 产生最高的功率转换效率，相应的电荷转移电阻最低，而基于 CuS/g-C3N4 CE 的电池为 7由于过量的 CuS 颗粒聚集，循环时间表现出较差的光伏性能。优化后的 CuS/g-C3N4 CE 具有快速的电子转移和优异的电催化能力，这对于高性能 QDSC 至关重要。而基于 CuS/g-C3N4 CE 的 7 个循环次数的电池由于过量的 CuS 颗粒聚集而表现出较差的光伏性能。优化后的 CuS/g-C3N4 CE 具有快速的电子转移和优异的电催化能力，这对于高性能 QDSC 至关重要。而基于 CuS/g-C3N4 CE 的 7 个循环次数的电池由于过量的 CuS 颗粒聚集而表现出较差的光伏性能。优化后的 CuS/g-C3N4 CE 具有快速的电子转移和优异的电催化能力，这对于高性能 QDSC 至关重要。