Enhanced stability of organic thin films for electroluminescence by photoirradiation

Enhanced stability against heat and moisture in organic vapor-deposited TPD thin film having hole transport property has been achieved by UV irradiation. The crystallization of TPD film without any treatment was started within a week even at RT and accelerated with increasing temperature under the air. By photoirradiation using UV light, however, the TPD thin film was found to be difficult to form crystallized state and showed good contact with substrate even at 60 °C and in water for more than one month. Furthermore, the molecular interdiffusion by heat between organic layers in Alq3/TPD bilayer was remarkably suppressed by the UV irradiation due to the enhanced stability of the TPD film.