Rational design, synthesis, and characterization of a photocrosslinkable hole-transporting polymer for high performance solution-processed thermally activated delayed fluorescence OLEDs,Journal of Materials Chemistry C

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Rational design, synthesis, and characterization of a photocrosslinkable hole-transporting polymer for high performance solution-processed thermally activated delayed fluorescence OLEDs
Journal of Materials Chemistry C ( IF 5.7 ) Pub Date : 2020/02/26 , DOI: 10.1039/c9tc07107e
Ji Hye Lee _{1,

2,

3,

4,

5} , Cheol Hun Jeong _{1,

2,

3,

4,

5} , Mallesham Godumala _{1,

2,

3,

4,

5} , Chae Yeong Kim _{1,

2,

3,

4,

5} , Hyung Jong Kim _{1,

2,

3,

4,

5} , Jin Hyo Hwang _{1,

2,

3,

4,

5} , Yong Woo Kim _{6,

7,

8} , Dae Hyuk Choi _{6,

7,

8} , Min Ju Cho _{1,

2,

3,

4,

5} , Dong Hoon Choi _{1,

2,

3,

4,

5}

Affiliation

A new photocrosslinkable hole-transporting homopolymer (PX2Cz) was successfully synthesized using 9-((3-methyloxetan-3-yl)methyl)-9′-(4-vinylbenzyl)-9H,9′H-3,3′-bicarbazole monomer via radical polymerization. Biscarbazole, as a hole-transporting material, has two reactive sites that can introduce a radical polymerizable styrene moiety and a photocrosslinkable oxetane moiety. The photocuring temperature and time for the PX2Cz film was optimized to be 120 °C and 10 s. The photocured films showed good solvent resistance, which is favorable for the deposition of an emitting-layer solution on them. In particular, the highest occupied molecular orbital (HOMO) energy of the as-cast PX2Cz film was determined to be −5.37 eV which remained unchanged even after photocuring, thus facilitating hole transportation from the hole-injection layer. Subsequently, solution-processed, green, thermally activated delayed fluorescent organic light-emitting diodes (TADF-OLEDs) were manufactured using PX2Cz as the hole-transport material. The devices displayed a notable performance with an exceptionally low turn-on voltage (V_on) of only 2.8 V and a high external quantum efficiency (EQE) of 22.5%; these values are substantially better than those of commonly used poly(9-vinylcarbazole) (PVK)-based OLEDs (V_on = 3.6 V, EQE of 15.5%). The remarkably low turn-on voltage and high EQE were ascribed to the shallower HOMO energy level and more pronounced hole-transport ability of the photocured PX2Cz film.

中文翻译：

用于高性能溶液处理的热活化延迟荧光OLED的可光交联的空穴传输聚合物的合理设计，合成和表征

一种新的可光交联的空穴传输均聚物（PX2Cz）使用成功地合成9 - （（3-甲基吡啶-3-基）甲基）-9' - （4-乙烯基苄基）-9 ħ，9' ħ -3,3'-联咔唑单体通过自由基聚合。联咔唑作为空穴传输材料，具有两个反应位点，可以引入自由基可聚合的苯乙烯部分和可光交联的氧杂环丁烷部分。将PX2Cz膜的光固化温度和时间优化为120°C和10 s。光固化膜显示出良好的耐溶剂性，这有利于在其上沉积发光层溶液。特别地，铸态PX2Cz膜的最高占据分子轨道（HOMO）能量被确定为-5.37eV，其即使在光固化后也保持不变，从而有利于从空穴注入层的空穴传输。随后，使用PX2Cz作为空穴传输材料，制造了经过固溶处理的绿色热激活延迟荧光有机发光二极管（TADF-OLED）。V _on）仅2.8 V，22.5％的高外部量子效率（EQE）；这些值大大优于常用的基于聚（9-乙烯基咔唑）（PVK）的OLED（V _on = 3.6 V，EQE为15.5％）。较低的导通电压和较高的EQE归因于光固化PX2Cz膜的HOMO能级较浅，并且空穴传输能力更明显。

更新日期：2020-04-03

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