Organic nanocrystals induced surface passivation towards high-efficiency and stable perovskite solar cells

Surface passivation has played a critical role for efficient and stable perovskite solar cells by reducing surface defects, promoting charge transport, and preventing the penetration of degrading agents. State-of-the-art passivation approaches mainly rely on the formation of a two-dimensional (2D) perovskite layer or the deposition of an ultrathin layer based on the molecular design. Here, we demonstrated a novel nanocrystal-pinning passivation by dripping 2-bromoethyltrimethylammonium bromide (BETAB) colloidal solution onto perovskite films. Theoretical simulation and kinds of experimental results confirm that BETAB nanocrystals can effectively reduce the defect density of perovskite films. Impressively, the resulting FA1-xMAxPbI3 based planar devices exhibit a champion power conversion efficiency (PCE) of 23.04% (certified: 22.10%) with a voltage loss of only 390 mV. Besides, the BETAB nanocrystals could simultaneously increase the hydrophobic property of perovskite films and prevent the reaction and formation of 2D perovskites during device operation. Correspondingly, the resulted devices exhibit excellent stability under moisture, heating, and operational tracking conditions.

Automated summary

A novel nanocrystal-pinning passivation method using BETAB colloidal solution was demonstrated to effectively reduce the defect density of perovskite films, resulting in high efficiency and stability of perovskite solar cells. The resulting planar devices exhibited a champion power conversion efficiency (PCE) of 23.04%, with excellent stability under various conditions.