Importance of Bi–O Bonds at the 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 Cs 2 AgBiBr 6 double-perovskite films via a one-step spin-coating process and demonstrated a novel approach that modifies the surface of substrates with an ultrathin metal oxide (MO x ) 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 Cs 2 AgBiBr 6 films has remarkably risen up to ∼500 nm, which is nearly four times larger than the one directly deposited on a commercial fluorine-doped tin oxide 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 Cs 2 AgBiBr 6 film quality. The on–off ratio of the optimized PD has a boost of almost 10 times. In addition, the minimum detected irradiation has decreased from 9.7 × 10 –8 to 1.9 × 10 –9 W cm –2, as well as the maximum detectivity has increased from 3.3 × 10 11 to 1.2 × 10 13 Jones. These results suggest a feasible method for crystallization improvement of double-perovskite films and indicate promising promotion of photoelectric performance.