Highly efficient all fluorescent white organic light-emitting devices made by sequential doping

Abstract

Highly efficient all fluorescent white organic light-emitting devices (WOLED) have been fabricated by means of sequential doping. Fluorescent materials PT-01, PT-86 and PT-05 serve as the yellow guest, blue guest and fluorescent host, respectively. The emission layer consists of a few repeating cells, which are made of sequentially evaporated host and guest layers. From the analyses of the singlet exciton distribution and the influences of the thickness of the host layer, PT-86 and PT-01 are evaporated at the proper locations in the emission layer (EML), yielding a high efficiency and stable all fluorescent WOLEDs. The maximum current efficiency of the WOLED is 11.2 cd/A. In addition, the emission color of this WOLED is fairly stable, consistent with the Commission International de L’Eclairage coordinates, only showing changes (±0.004,±0.005) when luminance increasing from 159 cd/m2 to 20590 cd/m2. The devices based on the method of sequential doping not only have the similar performance compared with that fabricated by co-evaporation doping, but also have higher repeatability, which makes them appropriate for mass-production.