Proceedings of Technological Advances in Science, Medicine and Engineering Conference 2021

Mixed Anion Perovskites for photovoltaic applications – a first-principle study
Chapa Pamodani Wanniarachchi, Arunasalam Thevakaran, Punniamoorthy Ravirajan, Dhayalan Velauthapillai, Ponniah Vajeeston

In the field of photovoltaic research community of double perovskites solar cells acts a major role by considering their environmental issues and the matter of stability. Using density functional theory calculations, we study structural and electronic properties of double perovskites Cs2AgBiX6 (X = Br, Cl, F, I) as they belonged to Fm-3m (225) space groups of cubic or tetragonal phases. Structural stability and electronic structure analysis of all the compounds have been carried out using the VASP simulation package by using the exchange-correlation functional with generalized gradient approximation method (GGA) and hybrid functional (HSE06). Energy volume data are fitted with Birch-Murnaghan’s equation of state and equilibrium lattice parameters are obtained. Cs2AgBiX6 phases are stabilized in the cubic phase except for Cs2AgBiI6 and it stabilizes in the tetragonal phase. Electronic band structures and orbital-projected density of states of double perovskite materials were simulated. The calculated band gaps (Eg) were simulated using screened hybrid functional as proposed by Heyd, Scuseria and Ernzerhof (HSE06) for the polymorphs optimized at the PBE level and it is found as an indirect band gap. The calculated Eg in HSE06(GGA) for Cs2AgBiBr6, Cs2AgBiCl6, Cs2AgBiF6 and Cs2AgBiI6 are 1.97eV(1.35eV), 2.92eV(1.86eV), 4.27eV(2.75eV) and 1.21eV(0.83eV) respectively and they are in good agreement with the past theoretical and experimental investigations. We also evaluated the carrier mobilities of electron and holes along with the three directions of the first Brillouin zone G to K, G to L, and G to X  using effective mass calculations for the entire series. These theoretical results show the new approach to fabricate environmental friendly double perovskites solar cells alternative to the lead halide perovskites. 


Figure: Crystal structure of cubic (a) and tetragonal (b) structure of Cs2AgBiX6 phases. Octahedral BiX6 and AgX6  unites are highlighted with different color.

Keywords: Density functional Theory; Double perovskites; Photovoltaic


Last modified: 2021-06-27
Building: TASME Center
Room: Engineering Hall
Date: July 3, 2021 - 03:50 PM – 04:05 PM

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