Organic Electroluminescent Devices Fabricated with a Co-Deposited Hole Transport Layer

To improve the stability and durability of organic EL devices, the mixed HTL layer was fabricated by co-deposition of TPD and Alq3 and the EL cell with the mixed HTL was compared with that with the conventional pure HTL. When more than 5 wt% of Alq3 was added in HTL, the increase in surface roughness of IT0 I TPD-Alq3/Alq3 by annealing was found by AFM to be reduced dramatically. In addition, the running durability was significantly improved by addition of a small amount of Alq3 (< 10 wt %), although the EL characteristics of the cells with mixed HTLs were slightly lowered, i.e. I- V and L V curves shifted to the higher voltages.