Multifunctional interface modifier ammonium silicofluoride for efficient and stable all-inorganic CsPbBr3 perovskite solar cells

The interfacial modification has been considered as an effective strategy to build high-efficient and stable perovskite solar cells (PSCs) by reducing the loss of charge recombination and energy at electron transport layers (ETLs)/perovskite interface. Here, a multifunctional inorganic salt of ammonium silicofluoride (ASF) is utilized as an interfacial modifier to incorporate at TiO2 ETLs/CsPbBr3 perovskite interface, which decreases the surface oxygen vacancy defects of TiO2 by its bonding with silicofluoride anion and adjusts the energy level of TiO2 by dipole effect to minimize interfacial band difference, resulting in a promotion of electrons extraction and a reduction of energy loss. Simultaneously, the ASF modification affords a more hydrophobic TiO2 substrate for the constitution of perovskite film with larger crystal and passivates anion defects of CsPbBr3 film via the formation of hydrogen bonds between the H atom in ammonium cations and Br atom in perovskite, which dramatically inhibits the recombination of carriers. Finally, the all-inorganic CsPbBr3 PSCs based on the ASF-modified TiO2 ETL achieves a remarkable higher power conversion efficiency of 10.08%, compared to 6.84% efficiency of the control device. In addition, the long-term tolerance of the device without encapsulation towards high humidity and high temperature is significantly enhanced after interface modifying with ASF.