Indium tin oxide (ITO) is the prototypical transparent conductive oxide whose high conductivity arises from degenerate doping and conduction band filling. While ITO thin films have been extensively investigated, most studies of solution-processed films focus primarily on optical transparency and electrical resistivity, leaving a gap in the direct probing of the electronic structure that governs their electrical behavior. To address this research gap, this work aims to establish a comprehensive structural¿chemical¿electronic correlation study of ITO thin films deposited by ultrasonic spray pyrolysis within a narrow deposition temperature window (450¿500 °C). By combining X-ray diffraction (XRD), high-resolution X-ray photoelectron spectroscopy (HR-XPS), valence band spectroscopy, reflection electron energy loss spectroscopy (REELS), UV¿Vis spectroscopy, and four-point probe measurements, we directly identified lattice modifications, chemical composition, band structure evolution, and collective charge carrier dynamics. The novelty of our work lies in the direct observation of low-energy-loss features (~0.77 eV) and partial conduction band occupation via REELS, providing evidence of the Burstein¿Moss effect in spray-pyrolyzed films. We demonstrate that deposition temperature critically governs the balance between substitutional Sn incorporation and compensating Sn¿O bonding, thereby modulating charge-carrier density, plasmon energy, bandgap widening, and resistivity. The optimized film exhibits a band gap of 3.7 eV, a resistivity of 5.6 × 10¿3 ¿ cm, and 86% of transparency in the visible region. These characteristics are comparable to those of sputtered films, yet they are obtained via a low-energy process, such as spray pyrolysis.
