Sub‐Diffraction Nanolithography of Halide Perovskite via Reversible All‐Optical Crystallization–Decomposition

Abstract

ABSTRACT Halide perovskites exhibit exceptional optoelectronic properties, yet their intrinsic chemical fragility and ionic nature pose fundamental challenges for high‐resolution patterning and nanoscale integration. Here we report a reversible, all‐optical structural modulation strategy that enables chemistry‐free, sub‐diffraction patterning of halide perovskite thin films through light‐driven crystallization‐decomposition dynamics. Localized femtosecond laser excitation induces controlled crystallization and an orthorhombic‐to‐cubic phase transition in CsPbBr 3 thin films, markedly enhancing crystallinity and optoelectronic response. In contrast, ultraviolet illumination promotes defect formation and partial decomposition into CsBr and PbBr 2 , reversibly suppressing crystallinity and photocurrent. This optically driven crystallization‐decomposition cycle is repeatable over multiple iterations with more than 85% photocurrent recovery, establishing a robust platform for reversible material‐state control. Leveraging the nonlinear competition between laser‐induced crystallization and UV‐induced inhibition, we further demonstrate resist‐free, sub‐diffraction nanolithography with feature sizes down to 93.5 nm, well beyond the conventional optical diffraction limit. This work reveals a light‐programmable structural degree of freedom in halide perovskites and provides a general materials framework for reconfigurable perovskite architectures, adaptive photonics, and dynamic optoelectronic systems.