Exciton Regulation for Organic Light-Emitting Diodes with Improved Efficiency and Roll-Off by Managing the Bipolar Spacer Layers Based on Interfacial Exciplexes

Organic light-emitting diodes (OLEDs) based on interfacial exciplexes were early observed, whereas the unsatisfied efficiency and serious roll-off limit their practical applications owing to the poor luminous efficiency, a narrow exciton recombination region, and serious triplet-involved collisional quenching. Here, a highly effective approach is adopted to enhance the electroluminescence (EL) performance of interfacial exciplex-based OLEDs via simply modifying the spatially separated bipolar spacer layer to precisely manipulate the excitons and charges. As a result, based on a 1-bis[4-[N,N-di(4-tolyl)amino]phenyl]-cyclohexane/2,6-bis[3-(9H-carbazol-9-yl)phenyl]pyridine/2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine (TAPC-26DCzPPy-PO-T2T) system, the optimized orange OLED realizes the forward-viewing efficiencies of 24.0% and 76.0 lm W–1 for the external quantum efficiency (EQE) and power efficiency, respectively. The values of EQE are 2.4 and 1.7 times higher than those of devices based on interfacial and bulk exciplexes. The efficiency roll-off based on this system is also significantly improved. More excitedly, the TAPC-26DCzPPy-PO-T2T system can be not only used to enhance EL performance in phosphorescent and fluorescent OLEDs but also successfully applied to develop high-performance white OLEDs showing a high EQE of 23.7% and still keeping 21.7% at 1000 cd m–2. We believe that this study may shed light on the improvement of efficiency and its roll-off in the interfacial exciplex-based OLEDs.