Designing solution-processed thermally activated delayed fluorescence emitters via introducing bulky steric hindrance groups for pure red OLEDs

Abstract

Despite significant research progress in red TADF emitters, reports of highly efficient soluble pure red TADF emitters are scarce. Most reported red TADF emitters to date are designed with rigid acceptor units, rendering them insoluble and unsuitable for solution-processed OLEDs. To address this challenge, a novel approach of introducing bulky steric hindrance groups into acceptors is proposed, involving the design of tBuInPz-DQ and tBuInPz-SP TADF molecules. By strategically controlling intermolecular interactions, tBuInPz-SP, featuring a spiro-fluorene moiety, exhibits excellent quenching-resistant properties. Furthermore, OLEDs utilizing tBuInPz-SP show a 1.3–1.4-fold enhancement in external quantum efficiency (EQE) within the 650–675 nm DR emission range, with a maximum EQE of 3.4%. This work showcases a guiding approach to precisely manipulate intermolecular interactions of red TADF emitter molecules for solution-processed OLEDs.