Energy band tuning induced by g-C3N4 interface engineering for efficient and stable perovskite solar cells

Energy band tuning in perovskite solar cells (PSCs) was established via an interface engineering approach involving graphitic carbon nitride (g-C3N4) between TiO2 electron transport layer (ETL) and CH3NH3PbI3 perovskite absorber. The introduction of g-C3N4 resulted in simultaneous energy bands downshifts and conduction bands alignment to − 4.4 eV of the TiO2 and the perovskite, which facilitated the electron transfer to the anode without any energy loss and enhanced the short-circuit photocurrent density (Jsc). Moreover, the proposed modification provided a more hydrophobic substrate which favored the growth of perovskite films with better crystallinity and higher robustness against oxygen and humidity. The new strategy led to perovskite solar cells with an optimized overall photovoltaic performance including a power conversion efficiency (PCE) exceeding 20%. The g-C3N4 particles hindered perovskite degradation and the resulting PSCs retained 98% of their initial PCE after 3000 h under dark and relative low humidity (RH~20%) conditions.