Air-Stabled All Inorganic Lead-Free Perovskite Solar Cells*

Inorganic lead-free perovskite CsSnI₃ is an unusual sensitizer that has high electrical conductivity and exhibits near-infrared photoluminescence. However, the lack of chemical stability in air has limited its practical applications because it must be handled in an inert atmosphere when fabricating solar cells. In analogical compound Cs₂SnI₆, ion Sn in 4+ oxidation state which is stable in atmosphere have attracted great attention for its easy phase transition from CsSnI₃. Its direct bandgap at around 1.32 eV has made it a promising sensitizer used in perovskite solar cells (PSC). Both solid state reaction synthesis and solution process can be used. Spin coating Cs₂SnI₆ on anatase mesoporous TiO₂ forms a heterojunction structure followed by a hole transport material and a counter electrode.
We report a double layer metal doped TiO₂ mesoporous scaffold covered by the air-stabled semiconducting pigment to form a high efficient PSC through solution method. Doping metal elements into TiO₂ is expected to raise the mobility while extend the recombination time. The fabricated powder, thin films, and solar cells are characterized by UV-Vis spectrometer, EPR analysis, optical microscope, and photo-electricity property measurement.