EFFECTS OF PLASMA MODIFICATION ON HOLE TRANSPORT LAYER IN ORGANIC ELECTROLUMINESCENT DIODE

Crystallization of a diamine derivative (TPD), used as hole transport layer, could be successfully suppressed by plasma modification. Crystallization could not be observed in the plasma-modified TPD thin film after 30 days. The EL efficiency of the organic LED with a plasma-modified TPD layer was lower than that of conventional organic LEDs. This is explained by the quenching of Alq3 excitons due to the interfacial oxidation layer between emission layer and the plasma-modified TPD. The EL efficiency of the organic LED with a plasma-modified TPD layer was restored by the redeposition of TPD on the plasma-modified surf ace. However, although the crystallization of TPD was suppressed, the lifetime of the organic LED under the application of current could not be improved by plasma modification.