Fabricating CH3NH3Pb(SCN)2I Thin Film for Light Absorption in Hole Transporting Layer-Free Perovskite Solar Cells

Abstract

CH₃NH₃Pb(SCN)₂I (MAPb(SCN)₂I) perovskite thin films were fabricated by the Sequential Dip-Coating method on the titanium dioxide (TiO₂) surface. This process consists of two steps; first step, the thin Pb(SCN)₂ films were coated on the TiO₂ films using five different Pb(SCN)₂ concentrations (0.5 M, 1.0 M, 1.5 M, 2.0 M, 2.5 M, and 3.0 M), and the second step, the Pb(SCN)₂ films were dipped into the MAI solution for 2 mins. The surface morphology of MAPb(SCN)₂I films composes of the large polygon shape, and the films become more continuous with the increasing Pb(SCN)₂ concentration. The hole-transport-layer (HTL) free MAPb(SCN)₂I perovskite solar cells were assembled and tested. The carbon-based HTL-free MAPb(SCN)₂I perovskite solar cells prepared from the 1 M Pb(SCN)₂ film give the highest solar cell efficiency of 4.22%. This is because the MAPb(SCN)₂I film prepared from the 1 M Pb(SCN)₂ concentration has a relatively completed perovskite formation and the perovskite film almost covers the TiO₂ surface.