Solution-processed white OLEDs with power efficiency over 90 lm W−1 by triplet exciton management with a high triplet energy level interfacial exciplex host and a high reverse intersystem crossing rate blue TADF emitter

Abstract

Solution-processed white organic light-emitting diodes (WOLEDs) have shown much lower device efficiency than their vacuum-deposited counterparts, due to the lack of triplet exciton management in a single-emissive-layer device structure, which will induce triplet–triplet annihilation (TTA) and triplet-polaron annihilation (TPA). Here, two kinds of solution-processed WOLEDs, including thermally activated delayed fluorescence (TADF)/phosphorescence hybrid WOLEDs and all-TADF WOLEDs, with high power efficiency are developed by using a high triplet energy level (T₁) interfacial exciplex as a host and a high reverse intersystem crossing (RISC) rate TADF emitter as a blue dopant for triplet exciton management. The interfacial exciplex host with high T₁ can ensure that triplet excitons transfer from the host to the blue emitter, and the blue TADF emitter with high RISC rate (1.15 × 10⁷ s⁻¹) can rapidly upconvert triplet excitons to singlet ones to avoid TTA and TPA. The solution-processed TADF/phosphorescence hybrid and all-TADF WOLEDs exhibit maximum external quantum efficiencies of 31.1% and 27.3%, together with maximum power efficiencies of 93.5 and 70.4 lm W⁻¹, respectively, which are the record efficiencies for solution-processed WOLEDs, and quite comparable to those of most vacuum-deposited counterparts.