D3 永井勇次君（Yuji Nagai）のカルベン型純青色リン光発光材料に対するカルバゾールホスト材料群の影響に関する論文「Effect of Substituents in a Series of Carbazole-based Host Materials toward High-Efficiency Carbene-based Blue OLEDs」と題するの論文が、英国王立化学会(RSC) の J. Mater. Chem. C (IF: 5.066) にアクセプトされました。永井、おめでとうございます！
By Y. Nagai, H. Sasabe*, S. Ohisa, J. Kido*, J. Mater. Chem. C, accepted.
Abstract: In this work, we systematically investigated the effect of substituents in a series of carbazole-based host material toward blue OLED performances using a carbene-based phosphorescent emitter, mer-tris(N-dibenzofuranyl-Nʹ-methylimidazole)iridium(III) [Ir(dbfmi)]. As a host material, we used three types of 9-phenylcarbazole derivatives with triphenylmethane for 9-phenyl-3,6-ditrityl-9H-carbazole (CCz), triphenylsilane for 9-phenyl-3,6-bis(triphenylsilyl)-9H-carbazole (SiCz) and diphenylphosphine oxide substituents for 3,6-bis(diphenylphosphoryl)-9-phenylcarbazole (PO9), respectively. All the materials showed high triplet energy (ET) of 2.99 eV, which are 0.1 eV higher than that of Ir(dbfmi) (ET = 2.89 eV). Although these host materials can be expected to confine all the molecular triplet excitons of Ir(dbfmi) realizing a high photoluminescent quantum yield (hPL) and high-performance blue devices, co-deposited films of host:Ir(dbfmi) exhibited large differences in hPLs of 54–75%, and more surprisingly showed device performances with external quantum efficiencies (hext,max) of 9.5–21% depending on the substituents. These large efficiency losses are most likely caused by host-host aggregation, and inferior carrier balance of holes and electrons in the devices. However, by taking the advantages of the different optelectronic properties of these carbazole derivatives, we can successfully realized a blue OLED with a high power efficiency of 21.7 lm W-1, a low driving voltage at 3.40 V, and the Commission Internationale de l’Eclairage chromaticity coordinates (CIE) of (0.15, 0.18) at 100 cd m–2. These performances are among the highest in Ir(dbfmi)-based devices so far.
