Figure 1

Atomic Structures and optical properties of B-γ-CsSnI₃, Y-CsSnI₃ and Cs₂SnI₆.

(a) The XRD patterns of B-γ-CsSnI₃, Y-CsSnI₃ and Cs₂SnI₆. (b) Schematic representation of the phase changing processes from B-γ-CsSnI₃ to Y-CsSnI₃ and then to Cs₂SnI₆, red balls present “I”, yellow balls present “Sn” and blue balls stand for “Cs”. (c), (d) and (e) are UV-vis absorption spectra of Y- CsSnI₃, Cs₂SnI₆ and B-γ-CsSnI₃, respectively. (F(R)*hν)^α is proportional to absorption coefficient, where F(R) is the Kubelka-Munk function of reflection spectrum, R(v). The exponent, α, is equal to 2 and 0.5 for direct and indirect band-gap semiconductor, respectively. (f) The PL spectrum of B-γ-CsSnI₃ thin-film at room temperature.