A Highly Efficient, Blue-Phosphorescent Device Based on a Wide-Bandgap Host/FIrpic: Rational Design of the Carbazole and Phosphine Oxide Moieties on Tetraphenylsilane



A new series of wide-bandgap materials, 4-dipenylphosphine oxide-4′-9H-carbazol-9-yl-tetraphenylsilane (CSPO), 4-diphenylphosphine oxide-4′,4″-di(9H-carbazol-9-yl)-tetraphenylsilane (pDCSPO), 4-diphenylphosphine oxide -4′-[3-(9H-carbazol-9-yl)-carbazole-9-yl]-tetraphenylsilane (DCSPO), 4-diphenylphosphine oxide-4′,4″,4″′-tri(9H-carbazol-9-yl)-tetraphenylsilane (pTCSPO) and 4-diphenylphosphine oxide -4′-[3,6-di(9H-carbazol-9-yl)-9H-carbazol-9-yl]-tetraphenylsilane (TCSPO), containing different ratios and linking fashions of p-type carbazole units and n-type phosphine oxide units, are designed and obtained. DCSPO is the best host in FIrpic-doped devices for this series of compounds. By utilizing DCzSi and DPOSi as hole- and electron-transporting layers, a high EQE of 27.5% and a maximum current efficiency of 49.4 cd A−1 are achieved in the DCSPO/FIrpic doped device. Even at 10 000 cd m−2, the efficiencies still remain 41.2 cd A−1 and 23.0%, respectively.