Low threshold amplified spontaneous emission and lasing from single crystals and polymer microspheres based on a blue aggregation-enhanced emission molecule

Abstract

Organic semiconductors as a gain medium have attracted much attention in organic lasers due to their unique properties, i.e., large stimulated emission cross section, widely tunable spectrum region, and mechanical flexibility. Aggregation-caused quenching broadly exists in amorphous solid films and single crystals, which result in high threshold. Here, we studied amplified spontaneous emission (ASE) and lasing properties of an aggregation-enhanced emission (AEE) molecule, namely, 2PB-AC, who owns high photoluminescence quantum efficiency in a solid film and a single crystal. The grown long rod-like single crystals exhibited very good ASE characteristics with a threshold of 48 μJ cm−2 and a full width at half-maximum (FWHM) of 8.4 nm. Furthermore, when forming polymer microspheres by a surface tension-induced self-assembly method, a low lasing threshold of 0.32 mJ cm−2 and a FWHM of 0.41 nm were also obtained well, and their lasing modes could be modulated by changing the diameter of the microspheres. The investigations on transient photoluminescence dynamics and femtosecond transient absorption analysis demonstrated that the high radiative decay rate and the well separation between a stimulated emission band and an excited state absorption band are the main reasons of good lasing performance, indicating that AEE molecules are promising lasing materials.