First-principles investigation on the photovoltaic properties of lead free earth abundant (CH3NH3)2SnI6 perovskite

The issue of toxicity and chemical stability are two concerns for organic-inorganic hybrid perovskites, impeding their further commercial applications. Double perovskite (CH3NH3)(2)SnI6 with a bandgap of 1.81eV and stable chemical valence of Sn (+4) is considered as a promising alternative. By first-principles calculations, the electronic properties, defect physics, and interface engineering of the perovskite are investigated in this work. It is found that (i) MA(2)SnI(6) has a direct bandgap with a large dispersion of a lower conduction band. Due to the direct I 5p-5p transition between band edges, the light absorption can be as high as 10(5)cm(-1) in the visible range. (ii) An Sn rich and I poor condition is suggested when MA(2)SnI(6) is used as an electron transporting material (ETM) because of its high n-type electronic conductivity. An Sn poor and I rich condition is proposed when MA(2)SnI(6) is prepared for photovoltaic application, because it can suppress the formation of non-radiation centers. (iii) ICBA and Spiro are proposed to be suitable ETM and hole transporting material, respectively, in MA(2)SnI(6) based solar cells.

Automated summary

Toxicity and chemical stability are concerns for organic-inorganic hybrid perovskites, leading to the investigation of alternative CH3NH3)2SnI6. First-principles calculations reveal its electronic properties and conditions for different applications, such as electron transporting and photovoltaic. Suitable materials for use in MA(2)SnI(6) based solar cells include ICBA and Spiro as ETM and hole transporting material, respectively.