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

Abstract

Through passivating interfacial defects and improving energy level alignment and perovskite quality, ASF as interface modifier helps all-inorganic CsPbBr 3 PSCs achieve a champion PCE of 10.08% and excellent moisture and heat tolerance. • The interface modification of ASF passivates the defects of TiO 2 and perovskite. • The energy level alignment at TiO 2 /CsPbBr 3 interface is improved by modifying ASF. • A large-grained perovskite film is formed on the ASF-modified TiO 2 ETLs. • The ASF-modified CsPbBr 3 PSCs achieve a best PCE of 10.08% and excellent stability. 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 TiO 2 ETLs/CsPbBr 3 perovskite interface, which decreases the surface oxygen vacancy defects of TiO 2 by its bonding with silicofluoride anion and adjusts the energy level of TiO 2 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 TiO 2 substrate for the constitution of perovskite film with larger crystal and passivates anion defects of CsPbBr 3 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 CsPbBr 3 PSCs based on the ASF-modified TiO 2 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.