Breaking the Limit of Grain Boundaries in Perovskite Photodetection by High-Pressure Treatment

Grain boundaries (GBs) in polycrystalline metal halide perovskite (MHP) films hinder charge transport, limiting the optoelectronic device efficiency. Therefore, optimizing GBs and enhancing intergrain carrier transport is crucial for improving optoelectronic performance, especially in lateral-structure devices such as photoconductors, phototransistors, and photodetectors. Hydrostatic pressure provides a new dimension for tuning the structures and properties of halide perovskites. Here we report permanent structural changes, specifically recrystallization at GBs, and performance improvement of (FAPbI₃)_0.95(MAPbBr₃)_0.05 perovskite polycrystalline films by sustaining it under a mild pressure of 1.8 GPa for 12 h. The treated film, after being released to ambient conditions, exhibits a huge enhancement in carrier diffusivity by ∼5 times and photoresponsivity by ∼8 times. These notable enhancements are attributed to improved intergrain carrier transport facilitated by pressure-induced recrystallization at the GBs. These results imply that pressure treatment is a promising method for enhancing the optoelectronic performance of perovskite devices.