Enhanced Electroluminescence Based on a π-Conjugated Heptazine Derivative by Exploiting Thermally Activated Delayed Fluorescence

Frontiers in Chemistry

Qiang Guo¹  Lihua Jiang²  Li Tao³  Jie Li³  Shiyi Zhou³  Heqi Gong³  Jincheng Zhang³ 

[1] New Energy, Hubei Provincial Engineering Technology Research Center for Power Transmission Line, China Three Gorges University, Yichang, China;;College of Electrical Engineering &College of Optoelectronic Technology, Chengdu University of Information Technology, Chengdu, China;

关键词: electroluminescence;    heptazine;    thermally activated delayed fluorescence;    organic light-emitting diode;    exciplex;   

DOI  :  10.3389/fchem.2021.693813

来源: DOAJ

【 摘 要 】

Heptazine derivatives have attracted much attention over the past decade by virtue of intriguing optical, photocatalytic as well as electronic properties in the fields of hydrogen evolution, organic optoelectronic technologies and so forth. Here, we report a simple π-conjugated heptazine derivative (HAP-3DF) possessing an n→π* transition character which exhibits enhanced electroluminescence by exploiting thermally activated delayed fluorescence (TADF). Green-emitting HAP-3DF shows relatively low photoluminescence quantum efficiencies (Φp) of 0.08 in toluene and 0.16 in doped film with bis(2-(diphenylphosphino)phenyl) ether oxide (DPEPO) as the matrix. Interestingly, the organic light-emitting diode (OLED) incorporating 8 wt% HAP-3DF:DPEPO as an emitting layer achieved a high external quantum efficiency (EQE) of 3.0% in view of the fairly low Φp of 0.16, indicating the presence of TADF stemming from n→π* transitions. As the matrix changing from DPEPO to 1,3-di (9H-carbazol-9-yl)benzene (mCP), a much higher Φp of 0.56 was found in doped film accompanying yellow emission. More importantly, enhanced electroluminescence was observed from the OLED containing 8 wt% HAP-3DF:mCP as an emitting layer, and a rather high EQE of 10.8% along with a low roll-off was realized, which should be ascribed to the TADF process deriving from exciplex formation.

【 授权许可】

Unknown