A crystal-growth boundary-fusion strategy to prepare high-quality MAPbI3 films for excellent Vis-NIR photodetectors

Rendering high-quality perovskite films is integral for excellent performance of optoelectronic devices and highly challenging as well. Here, we establish a two-round pressure-assisted solvent-engineering (TPS) strategy to achieve remarkable enhancement in grain size (similar to 400 mu m(2)), crystallinity, orientation and, especially, boundary fusion. Crystal growth and boundary welding of MAPbI(3) grains are mainly attributed to pressure-enhanced ion diffusion and defect elimination, which facilitates lateral enlargement of grains and formation of ultra-smooth film. Dramatic diminution of trap density determines long carrier lifetime and improved lateral charge transport, as demonstrated by the superior performance of MAPbI(3)-based photodetectors, e.g. ultrahigh on/off ratio (similar to 10(6)), good stability, fast response, high responsivity and high detectivity (1.3 x 10(14) Jones). When upconversion nanoparticles are uniformly assembled on the high-quality MAPbI(3) films, interestingly, the hybrid device exhibits dominantly elevated photoelectric capability in near infrared range (NIR, 980 nm) with long-term stability in ambient air. The results and method pave a novel way for ongoing fabrication of efficient and stable optoelectronic devices based on high-quality perovskite films.