Benzochalcogenazolo-based N,O-coordinated boron difluoride complexes as gain media for organic solid-state lasers

Abstract

Three N,O-coordinated benzochalcogenazolo-based boron difluoride complexes have been designed, synthesized, and spectroscopically characterized using their solutions, solid state, and the films of dye-doped polymer. The structural analysis demonstrated that dyes adopt twisted molecular structures with the torsion angle ranging from 24° to 37°, attributed to the steric effect of cyano group. The obtained compounds exhibit aggregation-induced emission and blue to cyan emission (455–487 nm) in solid state with photoluminescence quantum yield ranging from 21% to 85% and short excited-state lifetime of 0.80–2.27 ns. These characteristics facilitate the amplified spontaneous emission (ASE) with the progressive reduction in full width at half maximum observed across the series of benzoxazole→benzothiazole→benzoselenazole derivatives up to 15 nm, 11 nm, and 8 nm, respectively, as well as the low ASE threshold values of 18.7–40.3 μJ/cm2. The successful application of the dyes in the fabrication of organic solid-state lasers results in the laser threshold of 46.1 µJ/cm2, 28.0 µJ/cm2, and 58.6 µJ/cm2 for the devices based on benzoxazole, benzothiazole, and benzoselenazole-based boron difluoride complexes, respectively. Our work opens the pathway for the novel class of heavy atom-containing organic laser dyes, which can be used for both organic optically and electrically pumped lasers.