<p>Alq₃ exists in five crystalline phases, with the δ-phase offering excellent charge transport characteristics owing to its minimal π-orbital overlap and short intermolecular binding distance. Previously, the purification of Alq₃ to obtain this specific phase was achieved using ionic liquids instead of sublimation methods. By controlling concentration and temperature, high-purity δ-phase Alq₃ could be obtained. In this study, the effectiveness of purifying Alq₃ using ionic liquids was examined not through high-performance liquid chromatography measurements but by fabricating and characterizing organic light-emitting devices (OLEDs) to assess improvements in purity and mobility. I–V–L measurements of the fabricated devices revealed a decrease in threshold voltage, an increase in maximum luminance, and a reduction in sub-threshold swing after purification. The I–V characteristics confirmed the effectiveness of ionic-liquid-based purification in enhancing material purity. Lastly, electron-only devices were fabricated, and charge mobility was calculated using the Mott–Gurney equation. The simulation and experimental results were compared to clarify the influence of δ-phase Alq₃ purified with ionic liquids on OLED performance.</p> Graphical Abstract <p></p>