Post-device Dimethylamine Treatment Enables Stable and Efficient Perovskite Solar Cells

The incorporation of organic ligands via post-device treatment is an effective strategy to improve the stability of perovskite solar cells (PSCs). Although the active area is protected by metal electrode under post-treatment, the aggression of post-treatment ligands into active area cannot be avoided thoroughly. Unfortunately, the size of long-chain amines is too large, and the three-dimensional (3D) perovskite cannot maintain its 3D perovskite structure once the cation substitution occurs during the post-treatment. Despite that the low-dimensional (LD) perovskites are beneficial to stability, long-chain amines are harmful to carrier transport in PSCs. Here, we introduce dimethylamine (DMA), a slightly oversized cation that can be doped into 3D perovskite structure, for post-device treatment to improve the efficiency and stability of PSCs. After exposure to DMA gas, the inactive area of Cs/FA/MA mixed cation perovskite device that is not covered by metal electrode is converted into LD perovskite, passivating the defects of 3D perovskite in the active region, suppressing non-radiation recombination and ion migration. As a result, we achieved a power conversion efficiency (PCE) of 22.29 % with negligible hysteresis and better stability after DMA post-treatment, which is much higher than that (20.40 %) of the control device.