Pressure‐Induced Topochemical Reconstruction for Quenchable Metastable ZnIn ₂ S ₄ With Enhanced Photoelectric Effect for Artificial Synapses Applica

ABSTRACT

Layered ternary sulfide ZnIn ₂ S ₄ is an attractive visible‐light semiconductor for photodetection, photocatalysis, and neuromorphic optoelectronics, but its photoelectric output is limited by inefficient carrier separation and sluggish carrier dynamics. Pressure offers a versatile route to reconstruct crystal and electronic structures, yet the enhanced properties generated under compression are usually lost after release. Here we report a pressure‐induced topochemical reconstruction in layered rhombohedral ZnIn ₂ S ₄ (3R‐ZnIn ₂ S ₄ ) that produces a quenchable metastable high‐pressure R 3 m phase (HP‐ R 3 m ). In‐situ photocurrent measurements show that the photocurrent density ( J _ph ), responsivity ( R ), and external quantum efficiency ( EQE ) increase by five orders of magnitude under pressure. Notably, the enhanced response still enhanced by approximately several tens of times after decompression. The transition from layered low pressure phase (LP‐ R 3 m ) to compact HP‐ R 3 m narrows the bandgap, lowers the resistance by orders of magnitude that suppresses photocarrier recombination for enhanced photoelectric behavior. At the same time, this enhanced photoelectric effect further enables pressure‐enhanced optoelectronic synaptic behavior, including paired‐pulse facilitation, pulse‐number‐dependent postsynaptic current, and prolonged forgetting time, which are useful for artificial synapses application. This work establishes pressure‐induced topochemical reconstruction as a promising strategy for creating quenchable metastable semiconductors with retained photoelectric and neuromorphic functions.