Hybridization of Long-Range and Short-Range Charger Transfer Enables Efficient Thermally Activated Delayed Fluorescent and Hyperfluorescent OLEDs

Abstract

Exploring possible strategy to balance the radiative decay and reverse intersystem crossing (RISC) are of great significance in thermally activated delayed fluorescent (TADF) emitters for enabling both high efficiency and low efficiency roll-off. Herein, by introducing a multi-resonance (MR) type acceptor, two TADF emitters featuring hybridized short-range charge transfer (SRCT) and long-rang charge transfer (LRCT) are designed. LRCT-dominate photoluminescent nature is maintained with a short delayed lifetime of 1.5–3.4 µs. While the incorporated SRCT accelerates the radiative decay. Consequently, both emitters demonstrate remarkable electroluminescent performance with maximum EQE (EQE_max) of 40.8% for IT-BO and 39.0% for IA-BO, respectively, along with ultra-high luminance of up to 120 000 cd m⁻². More encouragingly, both emitters can enable small efficiency roll-off with a minimum value of only 4%, highlighting the significance of enhanced k_r in suppressing the roll-off. Moreover, when served as sensitizers, both compounds can also endow excellent performances with EQE_max ≈38%. This work presents an innovative approach by hybridizing SRCT and LRCT for developing practical TADF emitters.