Nature of the band gap of halide perovskites ABX3 ( A = CH3NH3, Cs; B = Sn, Pb; X = Cl, Br, I): First-principles calculations*
Yuan Yea), Xu Runa), Xu Hai-Taoa), Hong Fengb), Xu Feib), Wang Lin-Juna)
       
Energy level of CBM and VBM of CsSnCl3 and CsSnI3.