Interfacial engineering designed on CuSCN for highly efficient and stable carbon-based perovskite solar cells

The undesired energy level alignment and charge recombination at the perovskite/carbon electrode interface limit the application of carbon-based perovskite solar cells (C-PSCs). The incorporation of hole transport materials, CuSCN, is an effective strategy to solve this issue. However, the mismatched crystal structure and lattice between the perovskite layer (cubic crystal) and CuSCN layer (hexagonal crystal) lead to a charge transport barrier due to the gaps at the heterogeneous interface. Herein, the interfacial engineering designed on CuSCN has been carried out, which not only improves the quality of perovskite film but also reduces the defects, enhances the interfacial connection, and ensures rapid charge extraction and transfer. After key parameter adjustment, both high efficiency (15.81%) and good stability of C-PSCs have been obtained. After storage for 2,000 h at ambient air environment, devices without any encapsulation could maintain 93% of their initial efficiency. The thermal stability test shows that the encapsulated devices retain 83% of their initial efficiency after storage for 300 h in dry air at 85 °C. Deep insight and mechanisms have been proposed in this interfacial engineering design for improving the efficiency and stability of C-PSCs.