Tuning optical properties of triphenylamine‐pyrrole by alkyl‐substituted thiobarbituric acid for dye‐sensitized solar cell

Abstract

Nonfullerene acceptors (NFAs) have been recently explored to tune the organic dye-sensitized solar cells. We designed three alkyl derivatives of NFAs from thiobarbituric acid (TBT1) decorated the triphenylamine featuring pyrrole unit (TPAP) to yield TPAP-TBT1, TPAP-TBT2, and TPAP-TBT3 for the potential activity in solar cell applications. Density functional theory (DFT) calculations using B3LYP level of theory and b3lyp/6-311g(d) basis set was used for the structures optimization. The TD-DFT calculations were performed for the structures orbitals (HOMO and LUMO) calculations. The electronic structures of TPAP-TBT2 derivative show the transethyl group on the structure, which facilitates the binding (−15.6 kcal/mol) to the semiconductor surface (TiO2) rather than the steric-hindered N-benzyl derivative (−13.1 kcal/mol). TBT alkyl substituents facilitate the intramolecular charge transfer within the dyes and improved the D-π-A electron mobility and the solar cell efficiency. The N-ethyl and N-benzyl derivatives showed better performance with respect to the calculated ΔGinject (−1.27) and (−1.22) and VOC values (1.45) and (1.40), respectively.