Morphology-controlled synthesis of CuCo ₂ S ₄ as a high-efficiency counter electrode <i>via</i> a precursor-directed strategy for quantum dot-sensitized solar cells (QDSSCs)

Quantum dot-sensitized solar cells (QDSSCs) have emerged as promising photovoltaic devices, in which the counter electrode (CE) plays a crucial role in the catalytic reduction of S_n ^2- and charge transfer. Based on a precursor-directed strategy, this study reports a simple and cost-effective solvothermal method for the synthesis of morphology-controlled CuCo₂S₄ nanomaterials without templates and structure-directing agents, including flower-like (f-CuCo₂S₄), nanosheet-like (n-CuCo₂S₄), nanoparticle-like (p-CuCo₂S₄), and microsphere-like (m-CuCo₂S₄) structures. The effects of CuCo₂S₄ CEs with different morphologies on the photovoltaic performance of QDSSCs were also systematically investigated. Among them, the f-CuCo₂S₄ CE exhibited the highest specific surface area and the best catalytic performance, resulting in a power conversion efficiency (PCE) of 7.42% for QDSSCs, which is 55% higher than that of materials with other morphologies. Electrochemical analysis confirmed that it delivered the lowest charge transfer resistance (<i>R</i> _ct = 0.076 Ω) and the highest electrocatalytic activity. This work highlights the importance of morphology control for optimizing the performance of CEs for efficient QDSSCs.