Theoretical study of optoelectronic performance of hole-transporting material quinoxaline-based with architecture (D-A-D) in perovskite solar cells: A DFT method

Developing ideal small-molecule hole-transporting materials (HTMs) is one of the most effective methods to improve the performance of perovskite solar cells (PSCs). Meanwhile, designing new molecules with theoretical chemistry methods and gaining a more fundamental understanding of the structure-property relationship is significant for developing highly efficient HTMs. In this study, new HTMs were designed based on quinoxaline core. Based on time-dependent density functional theory (TD-DFT) and density functional theory (DFT), the electron transfer mechanism was investigated by hole and electron analysis and inter-fragment charge transfer (IFCT). The results show that HTMs (TQ2, TQ3, TQ5, TQ7, and TQ8) exhibit suitable energy levels. The matched energy levels with MAPbI3 are helpful for the interfacial charge transfer. IFCT and hole-electron distribution indices show that TQ5 has a higher centroid distance (D = 1.74 Å), a greater degree of spatial expansion (H = 4.58 Å), the smaller overlap area (Sr = 0.62), the highest degree separation (t = −0.11 Å), more transmission of net charge (Q = 0.60 e−), and the highest hole contribution (71.38 %). Due to matched energy levels with MAPbI3, superior hole-electron distribution indices, good solubility, and better hole mobility, it is suggested that TQ5 has desirable properties as HTM in perovskite solar cells with (n-i-p) architecture.