Application of mixed interface in white-electrophosphorescent devices: An efficient approach to adjust the distributions of carriers

The distributions of carriers in white organic light-emitting devices can be tuned effectively by incorporating a mixed interface layer, consisting of 4,7-diphenyl-1,10-phenanthroline doped in N,N′-dicarbazolyl-4-4′-biphenyl. By adjusting the thickness and the BPhen concentration of the mixed interface, the optimal devices exhibit maximum current and power efficiencies of 20.9 cd/A and 19.9 lm/W, respectively, and slightly modified Commission Internationale De L’Eclairage coordinates, from (0.3174 0.3276) to (0.3141 0.3218). This is attributed to the good distributions of carriers between two emissive layers by inserting the mixed interface, thereby improving both the exciton formation probability and the charge transport balance.