Defect Passivation with Organic Co-Crystal Layers for Efficient and Stable Inverted Perovskite Solar Cells: A Non-2D-Perovskites Strategy for Surface Treatments.

Surface defects caused by the wet-chemical deposition method negatively affect the performance and stability of inverted perovskite solar cells (PSCs). It is common to post treat perovskite films with large-sized organic ammonium salts, which allow for the formation of 2D perovskites on top of the perovskite films. However, the low-dimensional perovskites feature a low charge carrier mobility and poor structural stability. To address these issues, we introduce an organic co-crystal layer rather than 2D perovskites on top of the perovskite film in this work. This co-crystal layer effectively passivates the surface defects through a reinforced hydrogen-bonding network, suppresses non-radiative recombination, enhances n-type semiconductor characteristics, increases electron mobility and facilitates charge carrier transport in the perovskite films. As a result, the PSCs based on this layer achieve a champion power conversion efficiency (PCE) of 26.35% with enhanced short-circuit current (J_SC) and open circuit voltage (V_OC). Furthermore, the nonencapsulated device exhibits excellent thermal and moisture-resisted stability, manifesting in 80% initial PCE retention under heat stress of 85°C for 1392 h and 88% initial PCE retention after exposure to air with ∼50% RH for 2040 h. This work provides a novel strategy to passivate the surface defects of perovskite films beyond the formation of 2D perovskites for inverted PSCs.