Urbach Tail Suppression in Bi-Doped MAPbBr ₃ Driven by Water-Assisted Morphological Engineering

Bismuth (Bi3+) doping lead halide perovskites modulates optoelectronic properties but often induces structural disorder and trap formation. Here, Bi-doped MAPbBr3 synthesized via a water-assisted dissolution-recrystallization route is systematically investigated. As-grown microcubes exhibit lattice contraction, pronounced band tailing, and quenched photoluminescence due to nonradiative recombination. Controlled water-mediated recrystallization drives morphology transformation into wire-like microstructures, promoting lattice relaxation, dopant redistribution, and defect passivation. Consequently, the Urbach tail is suppressed and radiative recombination is restored. Time-resolved photocurrent reveals faster and reversible photoresponses, highlighting water-induced morphological confinement as an effective strategy to reduce energetic disorder in doped perovskites.