First principles prediction of the carrier mobilities and optical properties of strained lead free perovskite Cs2SnX6(X=Cl, Br)

Cs 2 SnX 6 (X = Cl, Br) is non-toxic perovskite and fairly stable in air. However, the broad band gap limits its application. The strain is an effective way to regulate the photoelectrical properties. The calculation results show that unstrained Cs 2 SnCl 6 and Cs 2 SnBr 6 bulk are direct bandgap semiconductors with the band gap of 3.984 eV and 2.491 eV at Γ points. The band gap decreases under compressive strain and increases under tensile strain. Moreover, the electron and hole mobilities of unstrained Cs 2 SnCl 6 are 288.33 and 0.007 cm 2 V −1 s −1 , the electron and hole mobilities of unstrained Cs 2 SnBr 6 are 611.31 and 0.02 cm 2 V −1 s −1 . The carrier mobility is greatly enhanced by applying compressive strain. The reason is that the charge localization becomes weaker under compressive strain, resulting in better transmission. Besides, the compressive strains result in the band gap to become smaller, making the absorption edge of Cs 2 SnX 6 (X = Cl, Br) red shifted. Thus the strain can effectively tune the photoelectric properties and facilitate the application of Cs 2 SnX 6 (X = Cl,Br) perovskite. • The carrier mobilities of Cs 2 SnX 6 (X = Cl,Br) are greatly enhanced by applying compressive strain. • The strain can effectively tune the photoelectric properties and facilitate the application of Cs 2 SnX 6 (X = Cl,Br) perovskite.