Efficiency and Color-Temperature-stability Improvements in Exciplex-Based Phosphorescent Organic Light-Emitting Diodes with a Quantum Well Structure

Currently, exciplex has drawn a great deal of attention due to its potential for efficient electroluminescence and for use as a host. In this study, we used 4,4',4 ''-Tris(carbazol-9-yl) triphenylamine (TCTA) and 1,3,5-Tri(m-pyridin-3-ylphenyl) benze nee (TmPyPB) to form an exciplex host, where Bis[2-(4,6-difluorophenyl)pyridinato-C2, N](picolinato)iridium(III)(FIrpic) was used as the dopant to emit blue phosphorescent light. Additional FIrpic and Bis(1phenylisoquinoline) (acetylacetonate) iridium(III) emission layers were inserted in the proposed structure to investigate how the recombination area of carriers shifts with the increase of voltage. TCTA and non-doped FIrpic layers were then inserted in both sides of the emission layer to confine the carriers, and the thickness of the emission layer was also optimized to improve the current efficiency of the proposed devices. The efficiency of the devices was increased from 56 cd/A to 63.6 cd/A with the additional quantum well structure and an emission layer thickness of 15 nm. The current efficiency reported in this paper was fairly high as compared with other published data on blue-emission exciplex-based organic light-emitting diodes. In addition, the device with the quantum well structure exhibited purer blue-light emission, and the color temperature stability was also highly improved.