Blue emitting C2-symmetrical dibenzothiazolyl substituted pyrrole, furan and thiophene

Abstract

The synthesis and photophysical properties of pyrrole, furan and thiophene substituted in their 2 and 5 positions by 2'-benzothiazolyl moieties have been investigated. The three species show deep-blue fluorescence with maxima in the 444–450 nm region, originating from excited states of π–π * character. The photoluminescence quantum yields were found to be higher for the pyrrole and furan compounds, 0.42 and 0.47 respectively, compared to the quantum yield of the thiophene species, 0.21. Light Emitting Devices were fabricated using the pyrrole species as 4% dopant in a 4,4',4''-tri(9-carbazoyl) triphenylamine emissive layer, or the same pyrrole species as a neat film. In low concentration of dopant, the device is characterised by deep-blue emission with CIE coordinates of x = 0.182, y = 0.185; on the other hand, a neat film of the dopant produces almost white light emission with CIE x = 0.381, y = 0.400 but at a cost of quantum efficiency due to self-quenching effects.