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

Abstract

Based on a carbazole and tetramethylphenylene backbone, a new class of thermally activated delayed fluorescence (TADF) polymers has been designed and synthesized using 3,6diphenylacridine 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 (ΔE ST ) 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.

Recent advances in regulating the excited states of conjugated thermally activated delayed fluorescence polymers for high-efficiency OLEDs

“…In 2023, poly(DOPAcDSCz-TMP), poly(DOPAcBPCz-TMP) and poly(DOPAcNICz-TMP) were designed and synthesized, in which TADF units with different electron-withdrawing abilities are located into the side chains. 26 The Δ E ST for all polymers is as low as 68–165 meV. The corresponding PLEDs display sky-blue, green, and red electroluminescence with EQE max values of 12.5%, 16.5%, and 3.6%, respectively.…”

Recent Advances in Fluorescent Polymers with Color-Tunable Aggregate Emission

“…By employing different acceptor structures (diphenylsulfone, benzophenone, and N-phenylnaphthalimide) in conjunction with the donor group 3,6diphenylacridine, distinct TADF emission colors were observed (486, 519, and 624 nm, respectively). 104 5.2. TSCT Polymers with Delayed Fluorescence.…”

“…On the other hand, polymerization of monomers with D and A conjugated in the pendant position is also an alternative way to produce CT fluorescent polymers. By employing different acceptor structures (diphenylsulfone, benzophenone, and N -phenylnaphthalimide) in conjunction with the donor group 3,6-diphenylacridine, distinct TADF emission colors were observed (486, 519, and 624 nm, respectively) …”

Modulating Backbone Conjugation of Polymeric Thermally Activated Delayed Fluorescence Emitters for High‐Efficiency Blue OLEDs

“…An ideal TADF emitter should be able to achieve both high EQE and low efficiency roll-off simultaneously. [15,16] In this regard, the TADF conjugated polymers with emission ranging from green to red colors have achieved satisfactory results, [17][18][19][20][21][22][23] but the development of blue TADF conjugated polymers still falls far behind, [24][25][26][27] which is mainly due to the accumulation of long-lived triplet excitons at high current density, resulting in a rapid roll-off of device efficiency. [28,29] To facilitate an efficient RISC process for the utilization of triplet excitons, it is necessary to add host units to copolymerize with TADF units to adjust the energy gap between S 1 and T 1 .…”