A general strategy for the preparation of long lifetime fluorescent materials based on charge-separated states

Abstract

Long lifetime fluorescent materials combine the high quantum yield of fluorescent materials with the long luminescence lifetime of long afterglow luminescent materials, showing good application prospects in fields such as anti-counterfeiting and organic light-emitting diode. However, the preparation of delayed fluorescent polymer materials with simple chemical structure and simple components faces significant challenges. This article proposes a general strategy for preparing delayed fluorescent polymer materials. The strategy is to copolymerize the electron withdrawing monomer containing common electron withdrawing group, bromine group, acetyl group, aldehyde group and cyano group with the naphthalimide derivative monomer M2 containing electron donating group. Detailed research has also been conducted on the effects of the electron withdrawing ability of electron withdrawing groups and their distance from electron donating groups on their photophysical properties. The research results indicate that when the distance between the electron withdrawing group and the electron donating group is close, it is beneficial to generate long-lived delayed fluorescence. Meanwhile, the stronger the electron withdrawing ability of the electron withdrawing groups, the longer the delayed fluorescence lifetime of copolymers. For P3CHO-M2, the duration of afterglow can reach 1.04 s in air. Also, the delayed fluorescent lifetime and the quantum yield can achieve 15 ms and 60 %, respectively.