[13a-B11-1~10] 12.4 Organic light-emitting devices and organic transistors

△ [13a-B11-9] Enhanching the electroluminescent efficiency in blue TADF OLED by changing the position of nitrogen atoms in a pyrimidine/acridine conjugate

〇(M1)Kohei Nakao¹, Hisahiro Sasabe^1,2, Ryutaro Komatsu¹, Yuya Hayasaka¹, Junji Kido^1,2 (1.Yamagata Univ., 2.Yamagata Univ. ROEL)

Keywords:Organic light-emitting device, Thermally activated delayed fluorescene

In this work, we developed a series of pyrimidine/acridine-based blue thermally activated delayed fluorescence (TADF) emitters, and investigated the effect of the position of nitrogen atoms toward the electroluminescent efficiency in organic light-emitting devices. We used 4-phenylacridine as a donor unit, and trisubstituted pyrimidine as an acceptor unit. As a result, when 4-phenylacridine was introduced into 2-potision of pyrimidine unit to give Ac-46DPPM, the photoluminescent quantum efficiency yield (PLQY) of the Ac-46DPPM-doped bis[2-(diphenylphosphino) phenyl]ether oxide (DPEPO) film was observed to be 61 % with an emission peak at 454 nm. whereas, when 4-phenylacridine was introduced 4-position of pyrimidine unit to give Ac-26DPPM, the PLQY of the Ac-26DPPM-doped DPEPO was observed to be 81 % with an emission peak at 475 nm. Although the differences in chemical structure are very small, however, Ac-26DPPM-based OLED showed 1.6 times higher EQE of 18.6 % with much smaller efficiency roll-off than that with Ac-46DPPM (EQE 11.8 %). We would like to discuss the strucutre-property relationships among these pyrimidine/acridine conjugates in detail.