Pendant Homopolymer and Copolymers as Solution-Processable Thermally Activated Delayed Fluorescence Materials for Organic Light-Emitting Diodes

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• 作者：Zhongjie Ren ; Roberto S. Nobuyasu ; Fernando B. Dias ; Andrew P. Monkman ; Shouke Yan ; Martin R. Bryce
• 刊名：Macromolecules
• 出版年：2016
• 出版时间：August 9, 2016
• 年：2016
• 卷：49
• 期：15
• 页码：5452-5460
• 全文大小：586K
• 年卷期：0
• ISSN：1520-5835

文摘

Materials that display thermally activated delayed fluorescence (TADF) have recently been identified as the third generation emitters for organic light-emitting diodes (OLEDs). However, there are only a few reported examples of polymeric TADF materials. This study reports a series of polymers with an insulating backbone and varying ratios of 2-(10H-phenothiazin-10-yl)dibenzothiophene-S,S-dioxide as a pendant TADF unit. Steady-state and time-resolved fluorescence spectroscopic data confirm the efficient TADF properties of the polymers. Styrene, as a comonomer, is shown to be a good dispersing unit for the TADF groups, by greatly suppressing the internal conversion and triplet–triplet annihilation. Increasing the styrene content within the copolymers results in relatively high triplet energy, small energy splitting between the singlet and triplet states (ΔE_ST), and a strong contribution from delayed fluorescence to the overall emission. Green emitting OLED devices employing these polymers as spin-coated emitting layers give high performance, which is dramatically enhanced in the copolymers compared to the homopolymer. Within the series, Copo1 with a regiorandom ratio of 37% TADF units:63% styrene units displays the best performance with a maximum external quantum efficiency (EQE) of 20.1% and EQE at 100 cd m^–2 of 5.3%.