Department of Physics and Centre for Plastic Electronics , Imperial College London , London SW7 2AZ , U.K.
Molecular Materials and Nanosystems and Institute for Complex Molecular Systems , Eindhoven University of Technology , P.O. Box 513, 5600 MB Eindhoven , The Netherlands.
ACS Appl Mater Interfaces. 2018 Apr 4;10(13):11070-11082. doi: 10.1021/acsami.8b00243. Epub 2018 Mar 21.
We report a novel approach to achieve deep-blue, high-efficiency, and long-lived solution-processed polymer light-emitting diodes (PLEDs) via a simple molecular level conformation change of an emissive conjugated polymer. We introduce rigid β-phase segments into a 95% fluorene-5% arylamine copolymer emissive layer. The arylamine moieties at low density act as efficient exciton formation sites in PLEDs, whereas the conformational change alters the nature of the dominant luminescence from a broad, charge transfer like emission to a significantly blue-shifted and highly vibronically structured excitonic emission. As a consequence, we observe a significant improvement in the Commission International de L'Eclairage ( x, y) coordinates from (0.149, 0.175) to (0.145, 0.123) while maintaining high efficiency and improved stability. We achieve a peak luminous efficiency, η = 3.60 cd/A, and a luminous power efficiency, η = 2.44 lm/W, values that represent state-of-the-art performance for single copolymer deep-blue PLEDs. These values are 5-fold better than for otherwise-equivalent, β-phase poly(9,9-dioctylfluorene) PLEDs (0.70 cd/A and 0.38 lm/W). This report represents the first demonstration of the use of molecular conformation as a simple but effective method to control the optoelectronic properties of a fluorene copolymer; previous examples have been confined to homopolymers.
我们报告了一种通过简单的分子水平构象变化来实现深蓝色、高效率和长寿命溶液处理聚合物发光二极管（PLEDs）的新方法。我们在 95%芴-5%芳胺共聚物发射层中引入了刚性β相段。在 PLEDs 中，低浓度的芳胺部分作为有效的激子形成位点，而构象变化改变了主导发光的性质，从宽的、类似于电荷转移的发射转变为显著蓝移的、高度振动结构的激子发射。因此，我们观察到在保持高效率和改善稳定性的同时，国际照明委员会（CIE）（x，y）坐标从（0.149，0.175）显著改善至（0.145，0.123）。我们实现了峰值亮度效率η=3.60 cd/A 和亮度功率效率η=2.44 lm/W，这代表了单共聚物深蓝色 PLED 的最新性能。这些值比等效的β相聚（9,9-二辛基芴）PLED（0.70 cd/A 和 0.38 lm/W）高出 5 倍。本报告首次证明了分子构象作为一种简单但有效的方法来控制芴共聚物的光电性质；以前的例子仅限于均聚物。
