Low-temperature processed SnO2 compact layer for efficient mesostructure perovskite solar cells

SnO2 nanoparticle film has been synthesized via low- temperature (∼180 °C) solution-processing and proposed as compact layer in mesostructure perovskite-type solar cell (PSC). Low-temperature processed SnO2 compact layer (cl-SnO2) brings perfect crystal-lattice and band-gap matching between electron selective layer and FTO substrate and close interface-contact between cl-SnO2 and mesoporous TiO2 layer (mp-TiO2), which contributes to suppressing carrier recombination and optimizing device performance. In varied thickness cells, 70 nm cl-SnO2 device exhibits maximum power conversion efficiency (PCE). In order to further restrain photoelectron recombination and improve the photovoltaic performance, the surface modification of cl-SnO2 by SnCl4 aqueous solution has been carried out. The recombination behavior in the cell interior is greatly retarded via SnCl4 treatment and champion PSC after SnCl4 treatment has acquire PCE of 15.07%, which is higher than PCE of cl-TiO2 based PSC fabricated with same mp-TiO2 and perovskite procedures (13.3%). The stability of cl-SnO2 PSC via SnCl4 treatment has also been measured and its PCE reduces to 13.0% after 2 weeks in air.