Printable hole-conductor-free mesoscopic perovskite solar cells coupled with an ultra-thin ZrO2 interface layer for improved performance

Modulating the interface between the electron transport layer (ETL) and perovskite to minimize interfacial recombination is pivotal for developing efficient and stable perovskite solar cells. Here, we introduce an ultra-thin ZrO 2 insulating interface layer onto the inner surface of the mesoporous TiO 2 ETL via the chemical bath deposition in the zirconium n-butoxide solution, which alters the interface characteristics between TiO 2 and perovskite for the printable hole-conductor-free mesoscopic perovskite solar cells (p-MPSCs). The insulating ZrO 2 interface layer reduces interface defects and suppresses interfacial non-radiative recombination. Furthermore, the ZrO 2 interface layer improves the wettability of the mesoporous TiO 2 ETL, which favors the crystallization of perovskite within the mesoporous scaffold. Meanwhile, the device performance presents thickness dependence on the interface layer. While increased thickness improves the open-circuit voltage, excessive thickness negatively impacts both the short-circuit current density and fill factor. Consequently, an improved power conversion efficiency of 19.9% was achieved for p-MPSCs with the ZrO 2 interface layer at its optimized thickness.