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 (Delta EST) 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 mu s. 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.