Constructing a stable and high-performance counter electrode for QDSSCs by modifying Co3S4 hollow nanocages with CuCo–B alloy-nanosheets

Counter electrode (CE) is a key part of enhancing power conversion efficiency (PCE) and strengthening cyclic stability in quantum dot sensitized solar cells (QDSSCs). Consequently, searching for alternative and high-quality CE materials has far-reaching consequences for extending the lifetime, increasing utilization and even further achieving commercialization of QDSSCs. Herein, we put forward an idea that the Co₃S₄ hollow nanocages were coated with CuCo–B alloy-nanosheets, and efficient Co₃S₄@CuCo–B composite CE was prepared by in-situ reduction method, and applied to QDSSCs. Because of its three-dimensional hollow structure, the Co₃S₄@CuCo–B composite has a higher specific surface area, encourages electrolyte diffusion, and enhances QDSSC stability. Alternatively, the work function analysis shows that Co₃S₄ modified by CuCo–B enhances the driving force of interfacial electric field and promotes electron transfer. The photovoltaic performance of QDSSC assembled with Co₃S₄@CuCo–B composite CE has demonstrated competitive ability via implementing a PCE up to 8.27 %, J_sc = 26.45 mA cm⁻², V_oc = 0.683 V and FF = 0.46. Among them, the PCE of Co₃S₄@CuCo–B composite CE respectively has ∼14.4 % and 29.6 % enhancements in comparison with pure CuCo–B and Co₃S₄ CEs. And Co₃S₄@CuCo–B composite CE displays stable current density after 200 cycle tests, demonstrating excellent cyclic stability. This work suggests that Co₃S₄@CuCo–B composite lays the theoretical foundation for becoming a high-performance CE.