Donor-acceptor properties of cyanoacrylated oligothiophenes

Hybrid organic-inorganic setups are promising to achieve high power conversion efficiency for solar cells, including direct bonding molecule-substrate or dye-sensitized SCs. Recent works [1] propose sensitizing through cyanoacrylic termination of the organic moiety. We present a theoretical study of cyanoacrylated thiophene TC short oligomers, focusing on electronic properties. We adopt ab-initio many-body GW on top of hybrid DFT+HF [2,3] calculations, for 1 to 3 thiophene units, clean T and TC. Regarding the TC oligomers, we find that the highest occupied orbital H is more localized on the T-part, and the Ionization Potential is deeper by just 0.4 eV for 3TC relative to clean 3T, while the lowest unoccupied L is more localized on the C-part, bringing the first excitation H-L down (at GW level) by 1.5 eV. The next excited state relates to the L+1 which is again localized on the T-part, with excitation energy H-(L+1) very similar to the H-L of the 3T. Our results are consistent with [1] and point to good photo-conversion properties.
[1] F. Pandolfi et al., Org. Biomol. Chem. 17, 3018 (2019); [2] M. Pinheiro Jr et al. Phys. Rev. B, 92, 195134 (2015); [3] V. Blum et al., Comput. Phys. Commun. 180, 2175 (2009).