Effect of the relationship between the energy levels of host and guest on EL performance of phosphorescence organic light-emitting diodes

作者：Liu, Wei; Yao, Jingwen; Sun, Qian; Dai, Yanfeng; Yang, Dezhi; Qiao, Xianfeng; Zhu, Tengfei; Li, Qiang^*; Ma, Dongge^*

来源：Organic Electronics: physics, materials, applications , 2021, 93: 106128.

DOI：10.1016/j.orgel.2021.106128

• Organic light-emitting diodes
• Phosphorescence
• Host-guest
• Triplet energy level

In this work, we used five different fluorescent hosts and six phosphorescent guests to study the effect of the relationship between the energy levels of host and guest on the EL performance of phosphorescence organic lightemitting diodes (PHOLEDs). The experimental results show clearly that the difference between triplet energy levels of the used host and guest plays an important role, and the electron and hole injection barriers, respectively, from electron-transporting layer (ETL) and hole-transporting layer (HTL) into emitting layer (EML) and the mobility of ETL also have a certain influence. It can be seen that the triplet energy level of hosts should be higher than that of guests and the distance between them is as close as possible, ensuring the effective energy transfer from hosts to guests. Furthermore, it is also necessary to have low injection barriers into EML for electrons and holes, and high electron mobility of ETL, which guarantee electrons and holes injected effectively and evenly. This further explains the fundamental reason why the fabrication of high efficiency PHOLEDs must optimize the host, guest and match transporting layers. Our studies will help to establish better design rules for host-guest systems to achieve high performance PHOLEDs.

• 单位
  TEST; test