Asymmetric Spirobiacridine-based Delayed Fluorescence Emitters for High-performance Organic Light-Emitting Devices.

Recently, researchers have focused on thermally activated delayed fluorescence (TADF) for efficient future lighting and displays. Among TADF emitters, a combination of triazine and acridine is a promising candidate for realizing high-efficiency organic light-emitting devices (OLEDs). However, simultaneous development of perfect horizontal orientation (Θ = 100%) and an external quantum efficiency (EQE) of over 40% is still challenging. Here, to obtain insights for further improvements of a triazine/acridine combination, we developed various asymmetric spirobiacridine (SBA)-based TADF emitters with a unity photoluminescence quantum yield and high Θ ratio of over 80%. Furthermore, we studied the substitution effects of the triazine acceptor unit on the photophysical properties, including molecular orientations and OLED performance. The corresponding OLED exhibited sky-blue emission with a high EQE of over 30%.