Pioneering research on blue “hot exciton” polymers and their application in solution-processed organic light-emitting diodes

Abstract

An innovative novel category of polymeric hybridized local and charge-transfer (HLCT) blue materials prepared via solution processing has yet to be reported. This study introduces three polymers, namely PZ1, PZ2, and PZ3, incorporating donor–acceptor–donor (D–A–D) structures with carbazole functioning as the donor and benzophenone as the acceptor. To regulate the luminescence mechanism and conjugation length, carbonyl and alkyl chains are strategically inserted into the backbone. Theoretical calculation and transient absorption spectroscopy illustrate that the robust spin-orbit coupling between high-lying singlet excited states (S_m: m ⩽ 4) and triplet excited states (T_n: n ⩽ 7) of the polymers hastens and significantly heightens the efficiency of reverse intersystem crossing processes from T_n states. Furthermore, the existence of multiple degenerated frontier molecular orbits and significant overlaps between T_n and S_m states give rise to added radiative pathways that boost the radiative rate. This study marks a fundamental and initial manifestation of HLCT materials within the polymer field and provides a new avenue for the design of highly efficient polymeric emitters.