Abstract: All-inorganic lead-free Cs₂AgBiBr₆ double perovskite is a promising semiconductor for photodetection in daily life due to its outstanding photoelectrical properties, non-toxicity, and high stability. Compared with its organic-inorganic hybrid analogs, the fabrication method for Cs₂AgBiBr₆ is not well developed. Solution-processed Cs₂AgBiBr₆ films usually exhibit loosened morphology with small grains, many pinholes, and abundant nonradiative defects. In particular, the disordered arrangements of Ag/Bi cations are thermodynamically favorable in Cs₂AgBiBr₆, which contribute to the formation of self-trapped excitons and heavily restrict charge transport. Here in this work, a modified green antisolvent engineering strategy with phenethyl-ammonium bromide (PEABr) dissolved isopropyl alcohol (IPA) solution is developed to prepare high-quality Cs₂AgBiBr₆ films. The PEABr/IPA treatment results in compact morphology with enlarged grains and promotes the ordered arrangements of Ag/Bi cations with improved charge transport. Through optimization, the target self-powered photodetector exhibits a responsivity of 0.38 AW^-1, a specific detectivity of 1.9 × 10¹² Jones, a response time of 54/63 µs, and a linear dynamic range of 107 dB, which is among the best-performing self-powered photodetectors based on lead-free perovskites. Our work thus provides a facile and green fabrication method for high-performance optoelectronic devices based on eco-friendly Cs₂AgBiBr₆.

Key words: Lead-free Cs₂AgBiBr₆ double perovskites, Photodetector, Cation arrangement, Charge transport, Green antisolvent engineering