<p>Amorphous indium–gallium–zinc oxide (a-IGZO) thin-film transistors (TFTs) have attracted significant attention as promising driving devices for next-generation organic light-emitting diode (OLED) displays owing to their high electron mobility (&gt;10&#xa0;cm²/V·s), wide bandgap transparency, and compatibility with low-temperature fabrication processes (~400&#xa0;°C). Despite these advantages, a-IGZO TFTs suffer from pronounced electrical instabilities when subjected to prolonged electrical, thermal, and optical stresses, leading to threshold voltage (V_th) shifts, carrier mobility degradation, and deterioration of subthreshold swing. Such instabilities ultimately limit operational lifetime and hinder uniform luminance control in high-resolution OLED panels. In this study, we systematically investigate the fundamental degradation mechanisms governing device instability, including defect generation, charge trapping at the dielectric–channel interface, and photo-induced ionization processes. Based on these insights, we propose comprehensive reliability-enhancement strategies through material engineering, process optimization, and structural design. The effectiveness of each approach is comparatively analyzed to highlight their impact on long-term device performance, providing practical guidelines for achieving stable, high-performance oxide TFTs for OLED display applications.</p> Graphical Abstract <p></p>