Soluble polyimides containing red and green thermally activated delayed fluorescence units for white organic light-emitting diodes

Journal article, 2026

At present, the synthetic difficulty of white light-emitting polymers needs to be reduced, and their operational stability still requires further enhancement. In this work, a series of cardo polyimides (PI) containing green thermally activated delayed fluorescence (TADF) units on the main chain and red TADF units on the side chain, respectively, designated as PITFN-x (x = 0, 0.5, 1, 3, 5, 10, or 100), were synthesized via a facile method. Ultimately, the white light emission was achieved by adjusting the molar ratio of green/red TADF units in PIs. All PIs demonstrated outstanding thermal stability (Td > 448 °C, Tg > 343 °C) and excellent solubility in common solvents such as trichloromethane (TCM) and dichloromethane (DCM). Meanwhile, they maintained the photophysical characteristics of the corresponding small-molecule emitters. The non-doped OLED device using PITFN-10 as the emitting layer (EML) achieved a maximum external quantum efficiency (EQEmax) of 0.86% and a maximum brightness (Lmax) of 1185.9 cd/m². Moreover, the doped device using the 10 wt% PITFN-10 in CBP as the EML exhibited white light with CIE coordinates of (0.35, 0.34), an EQEmax of 1.94% and a Lmax of 1236.4 cd/m². This research offers a new design approach for developing white light-emitting materials with both facile synthesis and good thermal stability.