Concentration effects on spontaneous and amplified emission in benzo[c]fluorenes

Abstract

Deep-blue-emitting benzo[c]fluorene-cored compounds featuring twisted peripheral moieties for suppressed concentration quenching of emission were synthesized and investigated as potential materials for light amplification. This detailed study of the effect of concentration on the spontaneous and stimulated emission, excited-state lifetime and susceptibility to form aggregates obtained for different benzofluorenes, has enabled the understanding of the concentration dependence of the amplified spontaneous emission (ASE) threshold and revealed the optimal concentration for the lowest threshold. The weak concentration quenching accompanied by high fluorescence quantum yield (>40%) and radiative decay rate (>5 × 10(8) s(-1)) have enabled the attainment of the lowest ASE threshold in the neat amorphous film of benzofluorene bearing dihexylfluorenyl peripheral moieties. Aggregate formation was found to negligibly affect the emission efficiency of the benzofluorene films; however, it drastically increased ASE threshold via the enhanced scattering of directional stimulated emission, and thereby implied the necessity to utilize homogeneous glassy films as the lasing medium. Although the bulky dihexylfluorenyl groups at the periphery ensured the formation of glassy benzofluorene films with the ASE threshold as low as 900 W cm(-2) (under nanosecond excitation), they adversely affected carrier drift mobility, which implied a tradeoff between ASE and charge transport properties for the lasing materials utilized in the neat form. Such a low ASE threshold attained in air is among the lowest reported for solution-processed neat films. The low threshold and enhanced photostability of benzofluorenes against fluorene compounds in air show great potential for benzofluorene-cored molecular glasses as active media for lasing applications.

Simultaneous retrieval of optical gains, losses, and threshold in active waveguides

“…[40,[42][43][44][45][46][47] In addition, to avoid a bias towards our lab results, the method and GUI AgL were tested against ASE spectra obtained from several samples measured in the labs of independent researchers not related with the author. In particular, these latter samples were based on carbon-bridged oligo(pphenylenevinylene)s, [48] benzo[c]fluorene core molecular glasses, [49] and poly(9,9-dioctylfluorene) (PFO). [29] A total of more than 40 different data sets were analysed and the results were highly successful and satisfactory.…”

In Situ Generation of Allenes and their Application to One‐Pot Assembly of Functionalized Fluoreno[3,2‐b]furans by Calcium‐Catalyzed, Regioselective, 3‐Component Reactions

“…[ 2 ] Further, fluorenes fused with arenes or heteroarenes are known to exhibit interesting optoelectronic properties due to the presence of extended π‐conjugation. [ 3 ] Among these fused‐fluorenes (Figure 1), the synthesis of benzofluorenes has been well explored due to their critical importance. For example, fluostatin family of natural products exhibit dipeptidyl peptidases inhibition, antibacterial and antitumor activities.…”

Synthesis of Divergent Benzo[b]fluorenones through Cycloaromatization Reactions of 1,5-Enynols and 1,5-Diynols

“…Benzofluorenes have recently been applied as a building block in the biosynthesis of Kinamycin atypical angucyclines . Furthermore, the aromatic π-conjugated benzo­[ b ]­fluorene derivatives have been employed as active materials in optoelectronic devices due to their high luminescence quantum efficiency and good chemical stability . To date, literature reports for the synthesis of the tetracyclic core structure typically requires multiple steps and high temperature conditions. − As a result, functional group tolerance and chemoselectivity have always emerged as problematic issues.…”