Recent progress in circularly polarized multi-resonance thermally activated delayed fluorescence materials for organic light-emitting diodes

Circularly polarized luminescence (CPL) is of importance to advance science and technology with significant potential applications in information storage, spintronics and optoelectronic devices. Integrating CPL and the emission mechanism of thermally activated delayed fluorescence (TADF) has attracted considerable attention, because of their 100% internal quantum efficiency in theory and easily modified molecular structures for tunable photo-electrical properties. However, the typical donor-acceptor (D-A) architecture of CP-TADF emitters generally induces a broad emission profile with inferior color purity due to their large structural relaxation under the processes of excitation and emission. Recently, CP-multi-resonance (MR)-TADF emitters that concurrently display CPL activity, narrowband emission and high efficiency are emerging as the most suitable candidates for the next-generation organic light-emitting diode (OLED) display. In this review, the progress of CP-MR-TADF materials is reviewed in terms of the molecular design strategy, the common relationship between the molecular structures and optoelectronic properties, and their OLEDs performance. Finally, the opportunities and challenges in this research topic are discussed.