Influence of π-linker on pyrone-based hole transporting materials in perovskite solar cells

In this study, we designed four pyrone-based hole transport materials (HTMs) P1-P4 in perovskite solar cells (PSCs) and studied the effects of the benzene and thiophene groups on their performance. Based on density functional theory (DFT), we investigated the geometry, frontier molecular orbitals (FMOs), density of states (DOS), solvation free energy (ΔGsol), absolute hardness, electrostatic potential (ESP), and hole transport rates of all designed molecules. Time-dependent density functional theory (TD-DFT) was used to analyse the absorption spectra, charge density difference diagrams (CDD), heat map, D index, H index, Sr index, and exciton binding energy (Ecoul) of HTMs P1-P4 to examine their optical and electronic excitation features. The simulation findings demonstrate that the HTMs P1-P4 molecular energy levels match with the energy level of perovskite (MAPbI3). Additionally, all designed molecules have good stability and high hole transport rates. The UV-visible absorption spectra show that the designed HTMs can broaden the optical absorption range of PSCs in the visible light region. In addition, by increasing the length of π-linker can significantly improve the photoelectric properties of the HTMs. The designed molecules exhibit great electronic character, optical character, hole transport rates, and stability, which provide ideas for the future design of high-efficiency HTMs.