Synthesis of 2- and 4-substituted carbazole derivatives and correlation of substitution position with photophysical properties and device performances of host materials

A synthetic method to synthesize 4-substituted carbazole derivative was developed to study the effect of substitution position of carbazole on photophysical properties and device performances of host materials. Two high triplet energy host materials with substituents at 2- and 4-positions of carbazole were synthesized by the new synthetic approach. Substitution of electron withdrawing group at 2-position was better than the substitution at 4-position to stabilize energy levels and to improve hole transport properties. However, high glass transition temperature and high quantum efficiency were obtained in the carbazole based host material with substituent at 4-position.