Tuning the Electronic, Photophysical and Charge Transfer Properties of Small D-a Molecules Based on Thienopyrazine-Terthienyls by Changing the Donor Fragment: A DFT Study

Abstract

Four acceptor-donor organic conjugated molecules based on thieno [3,4-b]pyrazine-terthienyls were analyzed in order to explore the effect of the donor substituent on their molecular structures, electronic and optical properties. Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD/DFT) calculations were carried out employing the B3LYP hybrid functional in combination with the 6-31G(d,p) basis set. The results suggests that the addition of electron-donating substituents to the conjugated molecules can diminish their energy gap value, which is beneficial to the photon harvesting. The lowest-lying absorption spectra of compounds substituted with electron donor groups exhibited a red-shift and a high oscillation factor compared with the unsubstituted molecule. Additionally, the ionization potential (IP), electron affinity (EA), reorganization energy (λ) and open-circuit voltage (V oc ) of the molecules were evaluated. According to these values, the molecules show good photovoltaic properties, and efficient charge transfer for hole and electron and balanced charges.

Synthesis, crystal structure with free radical scavenging activity and theoretical studies of Schiff bases derived from 1-naphthylamine, 2,6-diisopropylaniline, and substituted benzaldehyde

“…This suggests that compound 1 (small ΔE) depicts an easy transition while compounds 2 and 3 (larger ΔE) are more thermodynamically stable. Although it has been reported that electron donor groups elevate the energy value of both HOMO and LUMO levels as noticeable for compound 3 with substituted isopropyl [55]. Thus, causing the reduction of ΔE as a result of the destabilization of the HOMO orbital.…”