Effect of structural modifications on the spectral and lasing characteristics of truxene-cored starbursts with/without diphenylamine end-cappers

Abstract

This study examined the effect of chemical modifications on the spectral and lasing characteristics of truxene-cored starbursts as gain media for organic lasers. A series of conjugated starburst materials, consisting of a truxene core and oligofluorene bridges with and without diphenylamine (DPA), namely, TrXD and TrX, were assessed as model molecules to investigate the influence of DPA on the photophysical characteristics and organic lasing behaviors. TrXD with DPA could effectively restrain the aggregation and greatly suppress the aggregation-induced emission quenching, yielding high photoluminescence efficiency. A higher radiative decay rate kr was observed for TrXD than for TrX, suggesting that DPA is beneficial for enhancing the radiative decay process. TrXD showed low amplified spontaneous emission thresholds of 2.1–4.3 μJ cm−2 with high net gain coefficients of 80–101 cm−1, rather low loss coefficients of 2.6–4.4 cm−1, compared with TrX. The best performance with a lasing threshold of 0.31 kW cm−2 was obtained for Tr3D, which was superior to that of Tr3 (0.86 kW cm−2). The molecular systems with DPA have a large potential as attractive molecules for organic lasers because of the superior lasing properties induced by kr.