Study on the influence of chain extension and substituent position on charge transport properties and optoelectronic properties based on 2,5-di(pyrazine-2-yl)furan derivatives

In this paper, the basic structure of 2,5-di(pyrazine-2-yl)furan (DPF) was initially designed to tune the charge transport properties and photoelectric properties of organic materials by chain extension. Through the calculation of recombination energy, the structure with the introduction of anthracene group (DPF-A) is a stable P-type material with the smallest recombination energy in terms of adiabatic ionization potential, so the chain extended molecule DPF-A was selected as the base for the study of substituent positions. While thiophene , trifluorinated acyl, and methoxy groups were introduced to design DPF-A series derivatives. Density functional theory with high computational accuracy was applied to investigate geometric structure, orbital energy levels, ionization energy, electron affinity energy, and recombination energy. The results show that the increase (decrease) of the HOMO (LUMO) energy level leads to the red (blue)-shift of absorption wavelength and fluorescence emission wavelength; the vertical ionization potential decreases and the vertical electron affinity potential increases, thus the hole and electron injection barrier decreases; the decrease of the hole/electron recombination energy improves the charge transport ability of the molecule. Moreover, the adjustment of thiophene orientation and the position of the introduced group has the potential to transform the p-type material into an n-type material, resulting in the enhanced electron injection ability.