Integrating the Emitter and Host Characteristics of Donor–Acceptor Systems through Edge‐Spiro Effect Toward 100% Exciton Harvesting in Blue and White Fluorescence Diodes

Abstract

AbstractHerein, by utilizing edge‐spiro effect to modulate intramolecular charge transfer and intermolecular interactions, emitter and host characteristic are integrated in simple donor–acceptor systems named SFInxTz. As emitter, SFI34pTz realizes true‐blue thermally activated delayed fluorescent (TADF) diodes with an external quantum efficiency (EQE) of 25.3% and Commission Internationale de L'Eclairage (CIE) coordinates of (0.15, 0.20). As host, it can endow the yellow devices with the maximum EQE about 18%. When SFI34pTz serves as both blue emitter and yellow host material in pure fluorescence white device, the maximum efficiencies are as high as 22.9% for EQE and 52.4 lm W−1 for power efficiency, and stable electroluminescence spectra are successfully realized with CIE coordinates of (0.32 ± 0.01, 0.42 ± 0.02). Above all, SFI34pTz manifests the effectiveness of the edge‐spiro strategy in developing host‐featured blue TADF dyes for high‐performance blue devices and white organic light‐emitting diodes (WOLEDs). More importantly, a novel blue–orange–blue sandwich device structure consisting of all‐TADF materials for high‐efficiency pure fluorescence WOLEDs is proposed.