Color Tuning in Thermally Activated Delayed Fluorescence Polymers with Carbazole and Tetramethylphenylene Backbone

Based on a carbazole and tetramethylphenylene backbone, a new class of thermally activated delayed fluorescence (TADF) polymers has been designed and synthesized using 3,6-diphenylacridine as the donor and diphenylsulfone, benzophenone, or N-phenylnaphthalimide as the acceptor. Benefitting from the enhanced electron-withdrawing capability of the acceptor, the charge transfer (CT) in the side chain is found to be strengthened gradually, thus leading to a significant bathochromic shift for the photoluminescence from 486 to 624 nm. In addition, the singlet–triplet energy splitting (ΔEST) is measured to be as low as 68–165 meV for all of the polymers, which enables them to realize the efficient delayed fluorescence with the delayed lifetimes of 1.4–27.4 μs. The corresponding PLEDs are fabricated via a solution processing, revealing sky-blue, green, and red electroluminescence with the peak external quantum efficiencies of 12.5, 16.5, and 3.6% as well as Commission Internationale de l'Eclairage coordinates of (0.22, 0.43), (0.37, 0.57), and (0.62, 0.38), respectively. The results clearly highlight the color tuning in TADF polymers with a carbazole and tetramethylphenylene backbone.