Enhanced catalytic CuCo2Se4/g-C3N4 nano-composites as counter electrodes for high-performance quantum dot sensitized solar cells

Counter electrode (CE) plays a crucial role in collecting external circuit electrons and catalyzing electrolyte reduction in quantum dot sensitized solar cells (QDSSCs). Hence, inquiry into alternative CE materials with low cost and high catalytic activity will have a profound impact on realizing the commercialization of QDSSCs. Herein, we reported the in situ growth of CuCo2Se4 nanoparticles on graphitic carbon nitride g-C3N4 nanosheets by a simple hydrothermal method to form CuCo2Se4/g-C3N4 series composites and their first application as efficient CE materials in QDSSCs. The CuCo2Se4/g-C3N4 composite has a better hierarchical structure with g-C3N4 nanosheets as the support carrier, which is conducive to reducing the agglomeration effect of CuCo2Se4 nanoparticles, accelerating electrolyte diffusion and enhancing the stability of the material. In addition, the CuCo2Se4/CN-2 composite combines the excellent catalytic performance of the ternary selenide CuCo2Se4 with the better flexibility of g-C3N4 to exhibit prominent photovoltaic performance in QDSSCs, achieving a power conversion efficiency (PCE) as high as 8.48%, Jsc = 24.46 mA·cm−2, Voc = 0.635 V and FF = 0.55. It is 29% higher than the PCE (6.54%) of QDSSCs equipped with pure CuCo2Se4 CE. A series of measuring and testing approaches containing EIS, Tafel polarization and CV cycle experiments confirm that CuCo2Se4/CN-2 CE has much higher catalytic activity and stability, which further indicates that CuCo2Se4/CN-2 composite can become a potential electrode material in the field of solar cells.