A DFT study of influence of dichloromethane solvent and electric field on light absorption and electronic properties of two Quinoxaline-based solar cells

Abstract

Geometric structure, molecular vibration, electronic and spectroscopic properties including frontier molecular orbitals, energy gap and global reactivity descriptors, Uv–vis absorption spectrum, charge separation degree, driving force of electron injection and generation and fluorescence lifetime of two D-A-π-A Quinoxaline-based indoline dyes, IQ4 and IQ22, were investigated theoretically in vacuum and dichloromethane (DCM) solvent by methods of density functional theory and time-dependent density functional theory, so as to gain more insight into the influence of DCM solvent and substitution of cyclopentadithiophene (CPDT) conjugated bridge for thiophene on photoelectric properties of the targets. Comparing IQ22 with IQ4, the larger dipole moment, narrower HOMO-LUMO energy gap and bathochromic shift in absorption benefit IQ22 optoelectric performance while weaker driving force of regeneration, smaller charge transfer rate, lower charge separation degree and shorter fluorescence lifetime are unfavorable to its photoelectric conversion properties. There are no significant differences of Jsc and Voc between title dyes based on the previous experiment, mainly due to the positive role and negative impact induced by substitution of CDPT into thiophene. Solvent effect caused by DCM makes the parameters more favorable to be applied in solar cells device.