Engineering optoelectronic properties of Cs2SnI6 using pressure.

Lead free perovskites such as Cs2SnI6 have been given significant attention due to their extravagant optoelectronic properties. In this study, we use first principles calculations to explore the evolution of structural, optical and electronic properties of Cs2SnI6 when it is exposed to external hydrostatic pressure. Our results indicate that Cs2SnI6 is far more compressible as compared to other perovskites, mainly Cs2AgInCl6 and CsPbI3. The compression of the lattice leads to a lowering of bond length which in turn results in a higher orbital overlap. The reduction of I-I bond length results in a drastic decrease in the band gap of the material. Similar to electronic properties, optical properties also show a high dependency on pressure. With the increase in pressure both the absorptivity coefficient and refractive index increase. These findings show that the application of external hydrostatic pressure can act as an effective strategy to modify the opto-electronic properties of such materials. [ABSTRACT FROM AUTHOR]