Utilization of hot excitons to fabricate high efficiency blue fluorescence organic light-emitting diodes

Organic light emitting diodes (OLEDs) are a new generation of display and lighting technology. The practical application requires OLEDs to have high efficiency, long life and low cost. By comparison, fluorescent OLEDs have the advantages of long lifetime and low cost, but the problem of low efficiency. Hot excitons and their utilization are effective methods to improve the efficiency of fluorescent OLEDs. This paper introduces our recent research results on blue fluorescent OLEDs by the design of device structures to efficiently utilize hot excitons. We have carried out detailed studies on mechanism and find that the internal conversion between triplet energy levels is the main loss channel of hot excitons. Through the strategic design of device structures, we have achieved a breakthrough in the efficiency of blue fluorescent OLEDs. The maximum external quantum efficiency was as high as 14.8% and kept 14.4% at the luminance of 1000 cd/m2.