Modulation of Amplified Spontaneous Emissions between Singlet Fluorescence and Triplet Phosphorescence Channels in Organic Dye Lasers. Issue 7 (19th June 2019) - Li, Shuai
Abstract: Organic gain materials (OGMs) currently used in dye lasers and organic thin‐film amplifiers are limited to singlet‐fluorescence molecules. Although heavy‐metal‐containing phosphorescent emitters enable highly efficient organic light‐emitting diodes, phosphorescent OGMs capable of light amplification by stimulated emission from triplet states remain largely unexplored. Demonstrated herein is the first phosphorescent dye laser from a pure organic luminescent rotor (1 ), composed of electron‐donating sulfide‐substituted difluoroboron (SBF2 ) and electron‐accepting nitrobenzene (NB) moieties. Furthermore, modulation of amplified spontaneous emissions (ASEs) between singlet fluorescence and triplet phosphorescence channels is achieved by adjusting the relative rotation (dihedral angle θ ) of the donor and acceptor moieties. Theoretical calculations and experimental results clarify that free and restricted rotor rotation regulates the T 2 state below and above the S 1 state, thus switching on and off the intersystem crossing from S 1 to the high‐lying T 2 for phosphorescence and fluorescence, respectively. Based on this strategy, methyl groups are added on the NB moiety to increase the steric hindrance in2, leading to tunable phosphorescence and/or fluorescence ASE. The results extend the scope of organic dye lasers and provide a strategy to develop phosphorescence OGMs capable of amplifying light through ASE from the triplet state. Abstract : The first phosphorescence‐amplified spontaneous emission in solution from a pure organic luminescent rotor is demonstrated. Furthermore, modulation of ASEs between singlet fluorescence and triplet phosphorescence channels is achieved by adjusting the relative rotation of the donor and acceptor moieties. Methyl is added in the molecule to increase the steric hindrance, leading to tunable phosphorescence or fluorescence dye ASEs.