Effect of Li(+) Doping on Photoelectric Properties of Double Perovskite Cs(2)SnI(6): First Principles Calculation and Experimental Investigation

Double perovskite Cs(2)SnI(6) and its doping products (with SnI(2), SnF(2) or organic lithium salts added) have been utilized as p-type hole transport materials for perovskite and dye-sensitized solar cells in many pieces of research, where the mechanism for producing p-type Cs(2)SnI(6) is rarely reported. In this paper, the mechanism of forming p-type Li(+) doped Cs(2)SnI(6) was revealed by first-principles simulation. The simulation results show that Li(+) entered the Cs(2)SnI(6) lattice by interstitial doping to form strong interaction between Li(+) and I(−), resulting in the splitting of the α spin-orbital of I–p at the top of the valence band, with the intermediate energy levels created and the absorption edge redshifted. The experimental results confirmed that Li(+) doping neither changed the crystal phase of Cs(2)SnI(6), nor introduced impurities. The Hall effect test results of Li(+) doped Cs(2)SnI(6) thin film samples showed that Li(+) doping transformed Cs(2)SnI(6) into a p-type semiconductor, and substantially promoted its carrier mobility (356.6 cm(2)/Vs), making it an ideal hole transport material.