Spectroscopic Visualization of Polarons and Intervalence Charge Transfer in MoO3–x Nanostructures Via Defect Engineering

The emergence of quasiparticles in interacting matter is a fundamental aspect of contemporary physics, driving the pursuit of novel particles or phenomena that could shed light on mechanisms and improve photocatalytic and photoelectrocatalytic efficiency of MoO₃. This work extensively studied structural, vibrational, and optical properties and lattice distortions by oxygen defects in MoO_3–x nanostructures. An additional Raman mode (∼1003 cm^-1) that appeared in α-MoO₃ nanobelts due to oxygen vacancies is also related to the morphology and crystallite size. Coupling between lattice distortions and charge carriers emerged as a polaron band (∼561 nm) in h-MoO₃ nanorods, red-shifted owing to Coulomb interactions during lattice relaxation. Color center formation substantiated redshift, and the crystal field effect explained visible region photoluminescence where intervalence charge transfer (IVCT) exhibited a large Stokes shift. Time-resolved photoluminescence investigations of IVCT and near-band-edge emissions provide a platform to develop future optoelectronic devices with much faster speed and response time.