High-efficiency solution-processed OLED based on trivalent europium complex by modifying the composition of the multiple-host system

Xiaofang Li; Jiaxuan Yin; Jingyu Wang; Ruixia Wu; Shuaibing Li; Weidong Sun; Liang Zhou

doi:10.3389/fchem.2022.965927

High-efficiency solution-processed OLED based on trivalent europium complex by modifying the composition of the multiple-host system

Front Chem. 2022 Sep 14:10:965927. doi: 10.3389/fchem.2022.965927. eCollection 2022.

Authors

Xiaofang Li^{1

2}, Jiaxuan Yin^{1

2}, Jingyu Wang^{1

2}, Ruixia Wu¹, Shuaibing Li^{1

2}, Weidong Sun¹, Liang Zhou^{1

2}

Affiliations

¹ State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, China.
² School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei, China.

Abstract

In this work, di-[4-(N,N-ditolylamino)-phenyl]cyclohexane (TAPC); 4,4',4″-tri (9-carbazoyl)triphenylamine (TcTa); 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole (CzSi); and 1,3,5-tri (m-pyrid-3-yl-phenyl)benzene (TmPyPB) were used to constitute the multiple-host system and fabricate solution-processed organic light-emitting diodes (s-OLEDs) with europium complex Eu(DBM)₃Phen (DBM, 1,3-diphenylpropane-1,3-dione; Phen,1,10-phenanthroline) as emitter. In order to determine the optimal composition of the multiple-host system, a series of devices with different light-emitting layers (EMLs) were fabricated and compared. Experimental results revealed that removing TmPyPB out of the multiple-host system greatly reduces the turn-on voltage, whereas the addition of TcTa to the multiple-host system helps facilitate the transfer of holes from TAPC to Eu(DBM)₃Phen molecules, thus increasing the recombination probability of carriers on emitter molecules. Finally, high performance solution-processed red OLED (turn-on voltage of 3.8 V) based on the europium complex doped multiple-host system obtained the maximum current efficiency of 2.07 cd A^-1, power efficiency of 1.54 lm W^-1, external quantum efficiency of 1.2%, and brightness of 945 cd m^-2.

Keywords: host materials; multiple-host system; organic light-emitting diodes; recombination zone; solution-processed method.