A novel spiro-annulated host based on carbazole with good thermal stability and high triplet energy for efficient blue and green phosphorescent organic light-emitting diodes

A novel spiro-annulated host based on carbazole was synthesized and fully characterized. The thermal, photophysical and electrochemical properties of this host material were investigated. The host exhibited good thermal stabilities with a decomposition temperature of 427 degrees C and also exhibited excellent morphological properties. A high triplet energy (2.90 eV) was obtained for the host due to its spiro-annulated structure. This host was proved to be effective for both blue and green phosphorescent organic light-emitting diodes. Four different blue devices were fabricated with the best performance that a maximum current efficiency of 12.2 cd A(-1) and a maximum power efficiency of 8.8 lm W-1. The performance of the host was better than that of 4,4'-bis(9-carbazolyl)-biphenyl which is the benchmark host material in green PHOLED devices. (C) 2015 Elsevier Ltd. All rights reserved.