Composition, Morphology, and Interface Engineering of 3D Cauliflower‐Like Porous Carbon‐Wrapped Metal Chalcogenides as Advanced Electrocatalysts for Quantum Dot‐Sensitized Solar Cells

Abstract Designing a low‐cost, highly efficient, and stable electrocatalyst that can synergistically speed up the reduction of polysulfide electrolytes while operative for long periods in the open air is critical for the practical application of quantum dot‐sensitized solar cells (QDSSCs), but it remains a challenging task. Herein, a simple, straightforward, and two‐step nanocomposite engineering approach that simultaneously combines metallic copper chalcogenides (MC) either Cu_2−xS or Cu_2−xSe with S, N dual‐doped carbon (SNC) sources for devising high‐quality counter electrode (CE) film are reported. First, the hierarchically assembled MC nanostructures are obtained using microwave‐assisted synthesis. Second, these MCs are embedded within an ordered macro–meso–microporous carbon matrix to obtain Cu_2−xS@C or Cu_2−xSeS@C CE. These CEs are demonstrated to have composition dependents crystal structure, surface morphologies, photovoltaic performance, and electrochemical properties. In terms of power conversion efficiency (PCE), the Cu_2−xSeS@C (9.89%) and Cu_2−xS@C‐CE (8.96%) constructed QDSSCs outperform both Cu_2−xSe (8.96%) and Cu_2−xS‐constructed (7.79%) QDSSCs, respectively. The enhanced PCE could be attributed to the synergistic interaction of S and N dopants with MC interfaces that can not only enrich electric conductivity, and a higher surface‐to‐volume ratio but also offers a 3D network for superior charge transport at the interface.