Effect of fabrication conditions on photoluminescence and absorption of hole transport materials

It is well known that the performance of an organic light-emitting-diode (OLED) is affected by the fabrication condition. The OLED is more easily prepared than any other display device because it is prepared by vacuum deposition or a cast method. We changed the deposition rate at the same evaporation temperature by increasing the number of evaporation sources. The current-electroluminescence-voltage characteristics of OLED did not depend on deposition rate or evaporation temperature at the initial stage. Although all as-grown films prepared in various fabrication conditions showed an amorphous structure, the polycrystallization of films prepared at low evaporation temperatures progressed more slowly than at high evaporation temperatures. The polycrystallization of hole transport materials depended on evaporation temperature. (C) 2001 Elsevier Science B.V. All rights reserved.