ABSTRACT
Three m-terphenyl oxadiazole derivatives, 3,3â³-bis(5-(pyridin-4-yl)-1,3,4-oxadiazol-2-yl)-1,1':3',1â³-terphenyl (4PyOXD), 3,3â³-bis(5-(pyridin-3-yl)-1,3,4-oxadiazol-2-yl)-1,1':3',1â³-terphenyl (3PyOXD), and 3,3â³-bis(5-phenyl-1,3,4-oxadiazol-2-yl)-1,1':3',1â³-terphenyl (PhOXD), were synthesized. They exhibit relatively high electron mobilities compared with those of known electron-transport materials such as TAZ, BAlq, and BCP+Alq3. These materials were then utilized as electron transporters and hole/exciton blockers for blue, green, and red phosphorescent organic light-emitting diodes. The devices exhibited reduced driving voltages, very high efficiency, and negligible roll-off. More importantly, among these three oxadiazole derivatives, PhOXD performed as an ideal electron-transporting material for the blue, green, and red devices with excellent external quantum efficiencies (EQEs, >26%) as well as current and power efficiencies. Using these materials as an electron-transporting/exciton-blocking layer, low roll-off was achieved for the devices, indicative of excellent confinement of the triplet excitons in the emitting layer even at high current densities. At the normal operation brightness of 1000 cd m(-2), the EQEs remained >21.3% for these basic color devices. In addition, the relationships between physical properties and structures of the molecules such as the electron mobility, triplet energy gap, and efficiency can be clearly rationalized.
ABSTRACT
: In this study, direct-current magnetron sputtering was used to fabricate Ti-doped indium tin oxide (ITO) thin films. The sputtering power during the 350-nm-thick thin-film production process was fixed at 100 W with substrate temperatures increasing from room temperature to 500 °C. The Ti-doped ITO thin films exhibited superior thin-film resistivity (1.5 × 10-4 Ω/cm), carrier concentration (4.1 × 1021 cm-³), carrier mobility (10 cm²/Vs), and mean visible-light transmittance (90%) at wavelengths of 400-800 nm at a deposition temperature of 400 °C. The superior carrier concentration of the Ti-doped ITO alloys (>1021 cm-³) with a high figure of merit (81.1 × 10-³ Ω-¹) demonstrate the pronounced contribution of Ti doping, indicating their high suitability for application in optoelectronic devices.
