Fluorene- and benzofluorene-cored oligomers as low threshold and high gain amplifying media

Abstract

Deliberate control of intermolecular interactions in fluorene- and benzofluorene-cored oligomers was attempted via introduction of different-length alkyl moieties to attain high emission amplification and low amplified spontaneous emission (ASE) threshold at high oligomer concentrations. Containing fluorenyl peripheral groups decorated with different-length alkyl moieties, the oligomers were found to express weak concentration quenching of emission, yet excellent carrier drift mobilities (close to 10−2 cm2/V/s) in the amorphous films. Owing to the larger radiative decay rates (>1.0 × 109 s−1) and smaller concentration quenching, fluorene-cored oligomers exhibited down to one order of magnitude lower ASE thresholds at higher concentrations as compared to those of benzofluorene counterparts. The lowest threshold (300 W/cm2) obtained for the fluorene-cored oligomers at the concentration of 50 wt % in polymer matrix is among the lowest reported for solution-processed amorphous films in ambient conditions, what makes the oligomers promising for lasing application. Great potential in emission amplification was confirmed by high maximum net gain (77 cm−1) revealed for these compounds. Although the photostability of the oligomers was affected by photo-oxidation, it was found to be comparable to that of various organic lasing materials including some commercial laser dyes evaluated under similar excitation conditions.

Gain Properties and Distributed Feedback Laser Performance of 7F6/Poly(Styrene) Blend Films: Potential Core Material for Plastic Optical Fiber Expanding the Bandwidth to Visible Region

“…Nevertheless, the PLQYs of 70 wt% 7F6/PS blend film and the pristine 7F6 film are still higher than the PLQY of many blue emission polymers, such as PFO . The relatively lower PLQY of the pristine 7F6 film could be the result of concentration quenching due to high chromophore concentration, which is, however, essential for attaining high carrier mobility and for efficient lasing ultimately . Figure S2b in the Supporting Information shows the FWHM and output intensity of the emission spectra as a function of pump energy for the various 7F6/PS blend films.…”

Influence of Blending Ratio and Polymer Matrix on the Lasing Properties of Perylenediimide Dyes

“…1,2,21 Moreover, this issue reflects the importance of performing concentrationdependent studies when the PL and ASE performance of a given material is to be optimized. 4,5,[22][23][24][25][26] The ASE properties of PDI-O dispersed in PS as a function of the dye doping rate (up to 5 wt%) in PS were previously investigated. 4 It was found that the ASE threshold was kept at a low level (below 5 kW/cm 2 ) up to concentrations of around 3 wt%.…”

Enhanced Energy Transfer in Doped Bifluorene Single Crystals: Prospects for Organic Lasers

“…Following our previous studies, for production of crystals we selected fluorene‐based small molecules that were proved to be a successful gain media owing to their high radiative rate ( k r ≈ 1 ns −1 ) . In this work, to produce host–dopant crystals we employed bifluorene derivatives, where BF‐a (host) and BF‐e (dopant) differed only by modification of acetylene and ethylene bridging groups, respectively ( Figure a).…”