New bithiophene-based molecules as hole transporting materials for perovskite solar cells and or as donor for organic solar cells.

DFT and TDDFT approaches were used to design three (T_16,17,18) molecules based on 4,4'-dimethoxy-2,2'-bithiophene core to explore the influence of substitution of triphenylamine (TPA) fragment by methoxy groups, and introduction of azomethine π-bridges on the optoelectronic properties of hole transporting materials for perovskite solar cells (PSCs) or as donor for organic solar cells (OSCs). To shed light on the efficiency, stability, and solubility several physicochemical parameters were computed in dichloromethane solvent. All designed molecules show appropriate frontier molecular orbital levels, which facilitates effective hole transfer from the perovskite materials to the HTMs in the hole-transporting layer in PSC devices. They all show good efficiency and pore-fillings and are stable and soluble in dichloromethane. Electron-hole pairs can easily dissociate into free charge carriers, especially for T₁₆ and T₁₇; consequently, improve short-circuit current densities and facilitate hole transport. It is also advised to use T₁₈ which includes azomethine bridges as a donor with a non-fullerene Y6 acceptor to create effective OSCs because it exhibits high open circuit voltage, fill factor and low gap energy.