Rubrene-doped CuSCN composite hole transport layer toward high-efficiency and stable carbon-based perovskite solar cells

Carbon-based perovskite solar cells (C-PSCs) are promising for low-cost photovoltaic applications, but the insufficient hole transport capability and interfacial energy level mismatch of CuSCN hole transport layers (HTLs) remain critical bottlenecks. Herein, a facile solution-processed rubrene-doped CuSCN composite HTL is developed to address these challenges. Rubrene constructs continuous and efficient hole transport pathways in the CuSCN matrix, significantly enhancing hole mobility. It modulates the energy level structure to form a stepped alignment with both the perovskite active layer and carbon electrode, eliminating the hole collection barrier. Furthermore, rubrene induces an interfacial dipole moment at the buried perovskite/HTL interface, passivates copper vacancies in CuSCN and interfacial defects in perovskite, and suppresses trap-assisted non-radiative recombination. It also optimizes film-forming properties and alleviates the chemical corrosion of perovskite by diethyl sulfide. The optimal C-PSCs deliver a champion power conversion efficiency (PCE) of 16.26%, representing a 20.4% improvement over the control device. Unencapsulated devices retain 87.9% of their initial PCE after 1800 h of ambient room-temperature storage. This work provides a simple yet effective strategy for developing high-performance and stable C-PSCs.