Utilizing triazine/pyrimidine acceptor and carbazole-triphenylamine donor based bipolar novel host materials for highly luminescent green phosphorescent OLEDs with lower efficiency roll-off

作者：Braveenth Ramanaskanda; Ahn Dae Hyun; Han Ji Hun; Moon Ji Su; Kim Si Woo; Lee Hyuna; Qiong Wu; Kwon Jang Hyuk^*; Chai Kyu Yun^*

来源：Dyes and Pigments, 2018, 157: 377-384.

DOI：10.1016/j.dyepig.2018.05.022

• Organic light emitting diodes
• Bipolar host
• Green phosphorescent
• Triazine
• Pyrimidine

In this work, two novel bipolar host materials were designed, synthesized and applied in green phosphorescent based OLEDs. Both the host materials, 4-(2-(4,6-dipheny1-1,3,5-triazin-2-yl)-9H-carbazol-9-yl)-N,N-diphenylaniline (TRZ 1) and 4-(2-(4,6-diphenylpyrimidin-2-yl)-9H-carbazol-9-y1)-N,N-diphenylaniline (PYR 1) exhibited high thermal stability, with decomposition temperatures of 425 degrees C and 400 degrees C, respectively. The triplet energy of PYR 1 (2.63 eV) was higher than that of TRZ 1 (2.44 eV), and facilitated suitable energy transfer to the green dopant. The PYR 1 based green device demonstrated an excellent maximum current efficiency of 48.7 cd/A and external quantum efficiency of 16.4%. Interestingly, the green device with PYR 1 showed an outstanding brightness of 95,870 cd/m(2), which is three times greater than that of the reference CBP based device (31,370 cd/m(2)). The bipolar host PYR 1 is a promising material for high luminescent and low efficiency roll off applications, especially for green PhOLEDs.