Recent breakthroughs in non-conjugated polymers for thermally activated delayed fluorescent OLEDs: emitters, hosts, and hole-transport materials

Abstract

Recent advancements in the application of non-conjugated polymers as emitters, host materials, or hole-transport materials have significantly impacted the development of thermally activated delayed fluorescent (TADF) organic light-emitting diodes (OLEDs). Non-conjugated linkers between donors and acceptors (D–σ–A) demonstrate significant importance in OLEDs because they can hinder direct conjugation between the donor and the acceptor, which is advantageous for realizing blue emitters and high-triplet-energy (both hosts and hole-transport) materials. Moreover, TADF small molecules polymerized via a non-conjugated backbone have been proven to be potential polymers for thermally activated delayed fluorescence applications. Non-conjugated polymers used as hosts and hole-transport materials have also been developed, considerably enhancing the device performance of TADF-OLEDs. These polymers represent a highly attractive class of luminescent materials for TADF-OLEDs, offering numerous advantages, such as environmental sustainability, over their conjugated counterparts. In addition to their role in improving device performance, non-conjugated polymers offer tunable energy levels and molecular flexibility, enabling better control over charge transport and exciton dynamics. The versatile structural designs of these polymers make them ideal candidates for multi-functional components in OLEDs, including hybrid materials that combine TADF and other photophysical properties. Consequently, a comprehensive review describing the detailed design strategies along with synthetic routes for these polymers, applied as emitters, hosts, and hole-transport materials in TADF-OLEDs, is essential. Herein, the design tactics, along with the optoelectronic and electroluminescence properties of non-conjugated polymers reported to date, are comprehensively explained. The review concludes by emphasizing the transformative potential of these polymers in the TADF-OLED field and highlights the importance of continued research and development in realizing their full potential. By providing a systematic overview of the current state of research of non-conjugated polymers and identifying key areas for future investigation, this review serves as a valuable resource for researchers and industry professionals working in the organic electronics field.