Efficient Thiophene-Based Hole Transport Materials Containing Amide Groups as Bridges and Thiophene Derivatives as Acceptors for Perovskite Solar Cells

Abstract

Four thiophene-based organic molecules, A1–A4, featuring diverse thiophene central cores, triphenylamine side groups, and amide bridges, were designed as D-π-A-π-D type hole-transporting materials (HTMs) for use in perovskite solar cells (PSCs). The key characteristics of these HTMs were evaluated using DFT and TD-DFT methods, examining factors such as molecular planarity, frontier molecular orbitals, absorption spectra, optical emission, reorganization energy, density of states (DOS), stability, solubility, transition density matrix (TDM), and electron–hole contribution. According to our findings, the proposed HTMs demonstrated outstanding coherence in terms of charge carrier transit, dispersion, and excitation qualities that are perfectly suitable for strong hole mobility. Additionally, the results demonstrate excellent band alignment with the active perovskite layer with fitting HOMO energy levels. The acceptor anchor integration has significantly increased hole mobility in manufactured HTMs when compared to the reference named N5,N7-bis(4-(bis(4-methoxyphenyl)amino)phenyl)-2,3-dihydrothieno[3,4-b][1,4]dioxin-5,7-dicarboxamide EDOT-(Amide-TPA)2 (AR). This improvement is attributed to larger hole transfer integral values and decreased hole reorganization energy. Within the framework of produced HTMs, the transition density matrix and electron excitation analysis demonstrated stronger electronic coupling, more subtle charge carrier overlapping, and longer charge transfer lengths. In comparison to reference AR, this produced an excellent increase in intrinsic charge transference and a decreased exciton binding energy, which made exciton dissociation easier and reduced recombination deaths. Nonetheless, easy film formation and processability are guaranteed by a sufficient range in the dipole moment and Gibbs solvation-free energy. Our findings offer a molecular-level comprehension of creating HTM design strategies for effective photovoltaic features.