Donor–acceptor units modulate the electronic and photoluminescence characteristics of thiophene oligomers

Abstract

Organic small-molecule luminescent materials have high fluorescence quantum efficiency, are easy to purify, and show advantages related to brightness. However, the low mobility of hole carriers hinders their practical applications. To obtain luminescent materials with high fluorescence quantum efficiency, we investigated organic small-molecule thiophene oligomers with electron-donating or electron-accepting substituents at the terminal groups using the density functional theory. Compared with the electron-donating groups (–NH2, –CH3, –C2H5, and –C3H7), the electron-withdrawing groups (–NO2 and –COOH) resulted in unusual electronic and photoluminescent properties. The ultraviolet spectra of the thiophene oligomer derivatives could be modulated in the range of 200–500 nm, making them suitable for application in organic light-emitting devices. In particular, the group with the strongest electron-withdrawing effect (–NO2) resulted in blue light emission in the wavelength range of 400–480 nm, suitable for application in blue chips. Finally, the calculation results show that the donor–acceptor-modified oligomers are worthy of synthesis due to their relatively high electron mobilities.