CuS/g-C3N4 Composite as High-Performance Counter Electrode Materials in QDSCs

Abstract

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.