First-principles study on the structural, electronic and optical properties of vacancy-ordered double perovskites Cs_2PtI_6 and Rb_2PtI_6

摘要

In this paper, the structural, electronic and optical properties of vacancy-ordered double perovskites Cs2PtI6 and Rb2PtI6 were studied based on first-principles calculations. The stability of studied compounds is ensured by the negative formation enthalpy. The calculated results show that both Cs2PtI6 and Rb2PtI6 are indirect bandgap semiconductors. The bandgap values of Cs2PtI6 and Rb2PtI6 are 1.29 and 1.15 eV, respectively, which are suitable for photosensitive materials of solar cells. For both Cs2PtI6 and Rb2PtI6, the valence band maximum (VBM) is dominated by the I-5p orbitals and the conduction band minimum (CBM) is mainly composed of the I5p orbitals along with the Pt-5d orbitals. The optical properties of Cs2PtI6 and Rb2PtI6 in the photon energy range from 0 to 12 eV have been comprehensively studied by the HSE06 method. The results show that these two compounds exhibit excellent light absorption, especially in the ultraviolet range. Due to the suitable bandgaps and excellent light absorption, the vacancy-ordered double perovskites Cs2PtI6 and Rb2PtI6 can be effective candidates for lead-free photovoltaic materials.