High efficiency exciplex OLEDs based on thermally activated delayed fluorescence donor materials with a DMAC unit

In this work, three thermally activated delayed fluorescence (TADF) materials with the same DMAC core, namely DMAC-TRZ, DMAC-MPM and DMAC-DPS, were employed as donors to construct exciplex organic light-emitting diodes (OLEDs) with acceptor 3P-T2T. The exciplex OLEDs based DMAC-TRZ: 3P-T2T achieved the best performance, delivering a maximum luminance of 34740 cd/m 2 , current efficiency of 36.8 cd/A, power efficiency of 33.6 lm/W and external quantum efficiency of 11.5%, respectively. Interestingly, all three devices showed similar efficiency levels, indicating that the DMAC donor unit in the TADF materials plays a major role in forming high efficiency exciplex, rather than the overall molecular structure of TADF donor. The high efficiency of DMAC-core donor: 3P-T2T exciplex systems is attributed to dual reverse intersystem crossing (RISC) process, the intrinsic RISC of the TADF donor together with the RISC of the exciplex, which significantly enhances triplet exciton utilization. Furthermore, warm white OLEDs were successfully fabricated by doping Rubrene/DCJTB emitters into the DMAC-TRZ: 3P-T2T exciplex host, respectively. This work demonstrated the effect of donor molecular structure on the performance of exciplex, which provided a feasible strategy for designing heavy-metal-free, low-cost and high efficiency exciplex OLEDs.