The importance of Bi-O bonds at Cs2AgBiBr6 double perovskite/substrate interface for crystal quality and photoelectric performance.

Interface interactions between perovskite materials and substrates are of great significance for the development of high-quality perovskite materials. Herein, we have successfully prepared Cs2AgBiBr6 double perovskite films via one-step spin-coating process and demonstrated a novel approach that modifies the surface of substrates with ultra-thin metal oxide (MOx) layer to promote the film quality and photoelectric performance. Characterization results strongly suggest that the improvement is attributed to the Bi-O interfacial interaction at substrate/perovskite interface. Benefiting from this interface interaction, the average grain size of Cs2AgBiBr6 films has remarkably risen up to ~500 nm, which is nearly 4 times larger than the one directly deposited on commercial FTO substrate. Meanwhile, the pin hole surface area ratio has reduced from 2.61% to 0.60%. Furthermore, the corresponding photodetectors (PDs) have been fabricated and the performance has significantly improved owing to the enhanced Cs2AgBiB...