Synthesis of 5,6-dihydro[1,10]phenanthroline derivatives and their properties as hole-blocking layer materials for phosphorescent organic light-emitting diodes

Abstract

To develop new hole-blocking materials for phosphorescent organic light-emitting diodes (PhOLEDs), 5,6-dihydro-2,9-diisopropyl-4,7-diphenyl[1,10]phenanthroline (1) and 5,6-dihydro-2,9-diisopropyl-4-(4-methoxyphenyl)-7-phenyl[1,10]phenanthroline (2) were synthesized. While the absorption spectrum of I is very similar to that of 2, the photoluminescence spectrum of 1 has the feature of the narrower and blue-shifted blue-violet emission at the peak of 356 rim, compared to that of 2. The HOMO and LUMO energy levels of 1 and 2 were estimated from the measurement of cyclic voltanimetry, and 1 has the appropriate levels for a hole-blocking layer (HBL). The use of 1 as a HBL in a green PhOLED led to good efficiency of 23.6 cd/A at 4.4 mA/cm(2)..