Benzene substituted with bipyridine and terpyridine as electron- transporting materials for organic light-emitting devices

Article abstract of DOI:10.1039/c2jm16274a

New electron-transporting materials for organic light-emitting devices (OLEDs) based on trisubstituted benzene with both bipyridine and terpyridine, 1,3-bisbipyridyl-5-terpyridylbenzene (BBTB) and 1-bipyridyl-3,5- bisterpyridylbenzene (BTBB), were developed. Glass transition temperatures of BBTB and BTBB were 93 °C and 108 °C, respectively, and BTBB was completely amorphous with no melting point. Electron mobilities of BTBB exceeded the order of 10^-4 cm² V^-1 s^-1, while those of BBTB were very high and reached 10^-3 cm² V^-1 s^-1 at an electric field of approximately 500 kV cm^-2. These high mobilities contributed to a low voltage operation. For example, in the case of the conventional aluminum trisquinolinol (Alq)-based fluorescent OLED with BTBB, current densities of 3.5 mA cm^-2 and 100 mA cm^-2 were reached at voltages of 3.0 V and 4.5 V, respectively. In addition, ionization potentials of BBTB (6.33 eV) and BTBB (6.50 eV) were sufficiently large to confine holes in common emissive layers. The Royal Society of Chemistry 2012.