Enhancing performance and stability of perovskite solar cells through defect passivation with a polyamide derivative obtained from benzoxazine-isocyanide chemistry

Owing to the presence of amounts of defects in organic/inorganic hybrid perovskite, defect passivation is considered as a significant way to improve the efficiency and stability of perovskite solar cells (PVSCs). Herein, for the first time, a phenolic hydroxyl-substituted polyamide derivative (PAB), which was prepared by benzoxazine-isocyanide chemistry (BIC) and simultaneously contained hydroxyl, secondary amine, and carboxyl functional segments, was selected as the precursor additive to passivate perovskite active layer. Different passivation groups attached in the chain of a polymer are vital for the defect passivation of perovskite containing various defects. Hydroxyl and carboxyl can act as Lewis bases to passivate the undercoordinated lead defects, and secondary amine can coordinate with iodide ion. These passivation groups linked by the flexible polymer chains provide effective interaction with trap states on the surfaces and grain boundaries of perovskite, suppressing the trap-assisted non-radiative charge carrier recombination thus. As a result, these positive effects increased the efficiency of PVSCs from 19.45% to 21.13%, and maintained 95% initial efficiency after 32 days in ambient air (humidity around 50%, room temperature). This work opens a viable avenue to develop efficient passivating polymers via benzoxazine-isocyanide chemistry.