Efficient amplified spontaneous emission from oligofluorene-pyrene starbursts with improved electron affinity property.

A series of monodisperse starburst molecules as optical gain media have been investigated in detail. The starburst molecules were composed of a pyrene core with four short oligofluorene arms capped by cyanophenyl moieties. The compounds exhibited low amplified spontaneous emission (ASE) thresholds of 30 nJ pulse^-1 and high maximum net gain coefficient of 55 cm^-1 under optically pump. Our study demonstrates that the introducing of electron-withdrawing cyanophenyl end-capper onto pyrene centered starburst molecules does not disadvantage their optical gain properties while leading to reduced LUMO level, therefore, improved electron affinity. This study suggested a promising approach for organic gain material synthesis to address the challenge of electrically pumped organic laser.