Tailoring conjugated S doped g-C3N4 at the electron-transporting material/perovskite interface for carbon based perovskite solar cells

• S doped g-C 3 N 4 conjugated system was prepared via molecular design. • S doped g-C 3 N 4 was modified TiO 2 /MAPbI 3 interface. • The efficiency ranged from 9.26% to 12.67% in carbon-based perovskite solar cells . Perovskite solar cells have been promising energy materials due to their high photoelectric conversion efficiency, cost-effectiveness, and facile preparation process. However, the solution-based fabrication of perovskite thin films often introduces numerous defects and grain boundaries, which impede charge carrier transport and subsequently diminish device efficiency. To address this issue, interface modification has emerged as a promising approach to enhance carrier transport by passivating defects within perovskite thin films and improving the overall efficiency of perovskite solar cells . Here, sulfur doped g-C 3 N 4 (S-CN) is employed as an interface modification layer for TiO 2 /CH 3 NH 2 PbI 3 (TiO 2 /MAPbI 3 ) carbon based perovskite solar cells. The introduction of S-CN facilitates coordinated interactions with Pb atoms, leading to the passivation of defects, enhanced carrier mobility, optimized the TiO 2 /MAPbI 3 interface layer, and fostered crystal growth of perovskite. This comprehensive approach results in a significant increase in photoelectric conversion efficiency, elevating it from 9.26% to 12.67%. Our research not only demonstrates the efficacy of S-CN as an interface modification material but also contributes valuable insights into rational design strategies for defect passivation that can advance the efficiency and stability of perovskite solar cells.