Management of exciton recombination zone and energy loss for 4CzTPN-based organic light-emitting diodes via engineering hosts

Abstract

The exciton recombination zone and energy loss of organic light-emitting diodes (OLEDs) with thermally activated delayed fluorescence (TADF) emitter 4CzTPN (1, 2, 4, 5-Tetrakis(carbazol-9-yl)-3, 6-dicyanobenzene) as the dopant are explored by engineering hosts. The results demonstrate that the exciton recombination zone is determined by the matching condition between hole and electron mobility of hosts. The shift of the recombination zone from cathode to anode side induces a blue-shift of the electroluminescent spectra. And energy loss can be reduced by well-matched carrier mobility and TADF feature of host as well as lower energy level offset between host and guest. Specifically, the exciplex-co-hosted device delivers the maximum current/power efficiency/external quantum efficiency of 29.06 cd·A−1/28.89 lm·W−1/8.86%, respectively, enhanced by more than 50% than the single-component-hosted devices. This study illuminates that controlling exciton recombination zone and energy loss via engineering hosts is a feasible strategy for developing high performance TADF OLEDs.