Theoretical and computational exploration of electronic structure, optical properties, open circuit voltage, and toxicity of perovskites solar Cell:(Cs2SiX6, X = Cl, Br, and I)

Abstract

Perovskites are presently being considered as a feasible choice for hole-transport materials in photovoltaic devices. One material that stands out among the options is Cs2SiX6, where X indicates Cl, Br, and I. This material is of special interest due to its potential as a lead-free alternative, offering a variety of halide options. Moreover, several experimental inquiries have exhibited favorable outcomes; nevertheless, their theoretical or computational framework is limited and insufficient. As a result, the present investigation has opted for the crystal Cs2SiX6 and synthesized Cs2SiX6, Cs2SiCl6, Cs2SiBr6 and Cs2SiI6 to examine their electronic structures and optical properties using the DFT functional. The electronic structure of Cs2SnBr6, was calculated using GGA with PBE functional, yielding a band gap of 2.434 eV. It should be noted that the experimental value of Cs2SnBr6 was 2.450 eV. Furthermore, the band gaps of Cs2SiCl6, Cs2SiBr6, and Cs2SiI6 were calculated by GGA with PBE to be 1.540 eV, 1.291 eV, and 0.261 eV, respectively. In this study, various pseudopotential techniques are employed to investigate the electrical structures. Five different densities functional theory (DFT) functionals are utilized to determine the most accurate functional. Additionally, the study focuses on the LDA, a unique junction photovoltaic material. In addition, the six optical properties, specifically absorption, reflection, refractive index, conductivity, dielectric function, and loss function, are calculated to provide additional understanding of material qualities in the presence of visual evidence. The utilization of the Density of States (DOS) and the Partial Density of States (PDOS) was employed in order to calculate the electronic structure and bonding properties. For a material to effectively operate as a single-junction photovoltaic, it is imperative that its band gap remains within the specified range of 0.261–1.540 eV. The materials being discussed are conserved within this designated range and employed for their intended purposes. In summary, our research yields strong evidence suggesting that the aforementioned materials lack carcinogenic qualities and demonstrate only moderate degrees of toxicity. In sharp contrast, it has been observed that perovskites containing lead exhibit considerably higher levels of toxicity.