Building a Charge Transfer Bridge between g-C₃N₄ and Perovskite with Molecular Engineering to Achieve Efficient Perovskite Solar Cells

Effective defect passivation and efficient charge transfer within polycrystalline perovskite grains and corresponding boundaries are necessary to achieve highly efficient perovskite solar cells (PSCs). Herein, focusing on the boundary location of g-C₃N₄ during the crystallization modulation on perovskite, molecular engineering of 4-carboxyl-3-fluorophenylboronic acid (BF) on g-C₃N₄ was designed to obtain a novel additive named BFCN. With the help of the strong bonding ability of BF with both g-C₃N₄ and perovskite and favorable intramolecular charge transfer within BFCN, not only has the crystal quality of perovskite films been improved due to the effective defects passivation, but the charge transfer has also been greatly accelerated due to the formation of additional charge transfer channels on the grain boundaries. As a result, the champion BFCN-based PSCs achieve the highest photoelectric conversion efficiency (PCE) of 23.71% with good stability.