Organic light‐emitting transistors (OLETs) are emerging as a type of multifunctional devices that integrate the electrical switching and the light‐emitting function. Among the various device structures, multilayer OLETs have shown superior performance due to their flexibility in structure design and material choice. However, multilayer OLETs usually work in the unipolar mode, resulting in extreme unbalance between the holes and electrons, restricting the further improvement of their performance. Here, an investigation of the hole blocking layer (HBL) is presented. The results show that a high electron mobility is not necessarily in a first place when choosing the HBL, while a deeper highest occupied molecular orbital level of the HBL can better facilitate the exciton recombination efficiency. By using bis[(4‐tert‐butylphenyl)‐1,3,4‐oxadiazolyl]phenylene instead of commonly used bathophenanthroline (Bphen) as the HBL, the external quantum efficiency (EQE) is more than doubled for a blue fluorescent OLET, and an EQE as high as 10.3% is achieved in a green phosphorescent OLET with a maximum brightness of ≈8000 cd m⁻². The findings in this work highlight the importance of carrier blocking in building high efficiency OLETs and might provide some guidance for their structure design and material choice.

中文翻译：

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探索空穴阻挡效应，提高多层有机发光晶体管的效率

有机发光晶体管（OLET）逐渐成为一种集成了电子开关和发光功能的多功能设备。在各种器件结构中，多层OLET由于其结构设计和材料选择的灵活性而显示出卓越的性能。但是，多层OLET通常以单极模式工作，导致空穴与电子之间极度不平衡，从而限制了其性能的进一步提高。在此，对空穴阻挡层（HBL）进行了研究。结果表明，选择HBL的时候，而更深层次的最高占据HBL的分子轨道水平可以更好地促进激子复合效率高电子迁移率不一定在首位。通过使用双[（4-叔丁基苯基）-1,3，⁻²。这项工作的发现突出了载流子阻塞在构建高效OLET中的重要性，并可能为其结构设计和材料选择提供一些指导。