High Efficiency Phosphorescent OLEDs based on the Heterostructured Light Emission and Charge Injection Layers

摘要

The light emitting efficiency and the stability of the phosphorescent devices, whose emission characteristics are strongly dominated not only by the energy transfer but also by the charge carrier trapping influenced by the heterostructured emissive layers and charge injection layer, are studied in terms of the charge injection behavior, carrier transporting mobility, and balancing of devices. The enhancement of the light emitting properties (higher efficiency and lower driving voltage) by use of heterostructures at emitting layer, either multilayers or mixing of hole- and electron-transporting materials (such as 4,4",4"-tris(N-carbazolyl)-triphenylamine); TCTA and bis(10-hydroxybenzo[h]quinolinate) beryllium; Bebq_2) was characterized. By a design of emitting layer structure for recombination, 30~501m/W efficiency of devices with Ir(ppy)_3 and conventional transporting layer was possible.