Effect of the position of nitrogen in pyridoindole on photophysical properties and device performances of α-, β-, γ-carboline based high triplet energy host materials for deep blue devices

Three carboline derivatives with nitrogen at different positions of the pyridoindole unit were synthesized and the effect of the position of nitrogen on the photophysical properties and device performances was investigated. beta-Carboline was effective in obtaining high triplet energy and stabilizing energy levels, while alpha-carboline was better than other carbolines in terms of quantum efficiency. However, gamma-carboline could not stabilize the LUMO level and low quantum efficiency was obtained.