Intermediate Phase Halide Exchange Strategy toward a High-Quality, Thick CsPbBr₃ Film for Optoelectronic Applications

Inorganic halide perovskite CsPbBr3 is emerging as one of the promising alternatives to the hybrid counterparts for optoelectronic applications owing to its upgraded stability. Yet, the inherently low solubility of a CsBr precursor material restricts the quality and especially the thickness of a solution-processed CsPbBr3 film, thus hindering the further optimization of device performance. Herein, we report a facile intermediate phase halide exchange reaction that can break the thickness limit of a solution-processed CsPbBr3 film, since it avoids the use of low-solubility CsBr. Furthermore, the CH3NH3I byproduct after halide exchange could trigger a beneficial Ostwald ripening process to promote grain coarsening in the film. Hence, the uniformly flat, pure-phase, and compact CsPbBr3 film composed of [100] preferential, microsized grains can be achieved. As a demonstration of its excellent optoelectronic features, the carbon-based, all-inorganic photodetector with such a favorable film yields a maximum photoresponsivity of 0.35 A W–1 and a specific detectivity of 1.94 × 1013 Jones coupled with a response time of 0.58 μs.