Constructing host-σ-guest structures to optimize the efficiency of non-doped solution-processed OLEDs

Abstract

Two novel host-σ-guest emitters based on a blue emissive thermally activated delayed fluorescence (TADF) unit were designed and synthesized. By grafting 4TCzBN onto common host materials, these neat films (4TCzBN-o-PhCz and 4TCzBN-o-mCP) emit strong fluorescence with 39.4% and 60.8% photoluminescence quantum yields (PLQYs), respectively. And the oxygen-bridge linked host can not only suppress the triplet exciton quenching between guest units, but also improve the carrier transport ability. Non-doped OLEDs based on emitters formed by a solution process exhibit a maximum external quantum efficiency (EQE) of 8.0%, 24.9 cd A⁻¹ current efficiency (CE) and low efficiency roll off. These results indicate that the device performance can be improved by constructing a host-σ-guest structure with the introduction of an o-bridge linked bipolar host. The strategy proposed in this paper may provide inspiration for the design of more efficient blue solution-processable TADF emitters.