Postripening Fabrication and Self‐Driven Narrowband Photoresponse of Large‐Grain, Phase‐Pure CsPbBr3 Films

Halide perovskites have shown high potential for developing self‐driven filterless narrowband photodetectors with the advantages of excellent color recognition, low cost, and simple design. Among the various perovskites, all‐inorganic perovskites are most promising for optoelectronic devices due to their unmatched thermal stability, but they are often more difficult to be fabricated into a phase‐pure form with large grain sizes. Herein, for the first time, a self‐driven all‐inorganic perovskite narrowband photodetector (PNPD) fabricated by a scalable postripening aerosol–liquid–solid deposition method in ambient conditions is reported. Significantly, simply applying a short thermal stress to a pristine film with heterogeneous phases and small grain sizes triggers Ostwald ripening and leads to more than tenfold enlarged grains of phase‐pure CsPbBr 3 with considerably improved optoelectronic properties. The self‐driven CsPbBr 3 ‐based all‐inorganic PNPD shows a narrowband response, with a peak responsivity of 106.6 mA W −1 , specific detectivity of 2.2 × 10 12 Jones at 535 nm, and a narrow full width at half maximum of only 15 nm, placing it among the best of its kind. The PNPD is also fast ( t rise / t fall = 3.9/3.21 ms) and stable (above 10 000 on/off switches). This work opens the path of tapping all‐inorganic perovskites for next‐generation optoelectronics with high performance and reliability.