title: A two-layer structured PbI2 thin film for efficient planar perovskite solar cells.
abstract: In this paper, a two-layer structured PbI2 thin film was constructed by the spin-coating procedure using a 0.80 M PbI2 solution in DMF and subsequent close-spaced vacuum thermal evaporation using PbI2 powder as a source. The bottom PbI2 thin film was compact with a sheet-like appearance, parallel to the FTO substrate, and can be easily converted to a compact perovskite thin film to suppress the charge recombination of the electrons of the TiO2 conduction band and the holes of the spiro-OMeTAD valence band. The top PbI2 thin film was porous with nano-sheet arrays, perpendicular to the FTO substrate, and can be easily converted to a porous perovskite thin film to improve the hole migration from the perovskite to spiro-OMeTAD and the charge separation at the perovskite/spiro-OMeTAD interface. The planar perovskite solar cells based on the two-layer structured PbI2 thin film exhibited a photoelectric conversion efficiency of 11.64%, along with an open-circuit voltage of 0.90 V, a short-circuit photocurrent density of 19.29 mA cm(-2) and a fill factor of 0.67.
authors.affiliation: School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230009, P. R. China. shicw506@foxmail.com.
authors.forename: Chao
authors.initials: C
authors.lastname: Ying
authors.forename: Chengwu
authors.initials: C
authors.lastname: Shi
authors.forename: Ni
authors.initials: N
authors.lastname: Wu
authors.forename: Jincheng
authors.initials: J
authors.lastname: Zhang
authors.forename: Mao
authors.initials: M
authors.lastname: Wang