High-Quality CHNHPbI Films Obtained via a Pressure-Assisted Space-Confined Solvent-Engineering Strategy for Ultrasensitive Photodetectors.

High-quality organic-inorganic hybrid perovskite films are crucial for excellent performance of photoelectric devices. Herein, we demonstrate a pressure-assisted space-confined solvent-engineering strategy to grow highly oriented, pinhole-free thin films of CHNHPbI with large-scale crystalline grains, high smoothness, and crystalline fusion on grain boundaries. These single-crystalline grains vertically span the entire film thickness. Such a film feature dramatically reduces recombination loss and then improves the transport property of charge carriers in the films. Consequently, the photodetector devices, based on the high-quality CHNHPbI films, exhibit high photocurrent (105 μA under 671 nm laser with a power density of 20.6 mW/cm at 10 V), good stability, and, especially, an ultrahigh on/off ratio (I/I > 2.2 × 10 under an incident light of 20.6 mW/cm). These excellent performances indicate that the high-quality films will be potential candidates in other CHNHPbI-based photoelectric devices.