Highly efficient organic light-emitting diodes based on donor-acceptor small molecules

The authors have fabricated highly efficient organic light-emitting diodes from donor-acceptor small molecules, 2-(4-methyl-quinolin-2-yl)-10-phenyl-phenothiazine (MQPTZ) and 2-(4-phenyl-quinolin-2-yl)-10-phenyl-phenothiazine (PQPTZ). Their devices turned on at $4.0\mathrm{V}$ and emitted strong green light near $510\mathrm{nm}$ . The maximum luminance of 60 000 and $55000\mathrm{cd}∕{\mathrm{m}}^2$ at $10.4\mathrm{V}$ and the maximum power efficiencies of 5.75 and $2.5\mathrm{lm}∕\mathrm{W}$ at $5\mathrm{V}$ were obtained from the MQPTZ and the PQPTZ, respectively. The overall performance of their devices in terms of current-voltage, luminance, and external quantum efficiency were discussed and compared with those from the device with tris-(8-hydroxyquinolineolato) aluminum.