Concentration effects on emission of bay-substituted perylene diimide derivatives in a polymer matrix

Abstract

Reduction of emission quenching in a gain medium based on a dye-doped organic matrix at high doping concentrations is of crucial importance for achieving efficient lasing with a low threshold. In this study, concentration effects on emission properties of bay-substituted perylene diimide derivatives, considered to be promising for lasing application, are reported. Dynamics of emission spectra, quantum yield, lifetime, amplified spontaneous emission, amplified spontaneous emission threshold and photostability of the bromo-, 2,4-di(trifluoromethyl)phenyl- and 4-pyridyl-substituted perylene diimide derivatives in polystyrene films are explored in a wide range of diimide concentrations from 0.06 wt % to 8 wt %. For comparison, emission properties of an unsubstituted perylene diimide derivative are also investigated. An importance of the bay substitution in the perylene diimides is emphasized through i) reduction of emission concentration quenching, which allows for 3–4 times higher doping levels as compared to the doping with an unsubstituted perylene diimide, ii) observation of amplified spontaneous emission at one order of magnitude higher concentrations with reasonable thresholds (up to 200–300 kW/cm 2), and iii) high photostability, which is one order of magnitude higher than that of other bay-substituted perylene diimides and various organic compounds. The results imply potential of the perylene diimide substitution at the bay position for tailoring molecular packing and emission properties via steric hindrance effects, and suggest the bay-substituted perylene diimides may be useful as active media for lasing applications.