Abstract
Inorganic double halide perovskites have a wide range of applications in low-cost photovoltaic and optoelectronic devices. In this manuscript, we have studied their structural, electronic, mechanical and optical properties using density functional theory (DFT) simulations. In this work, hydrostatic pressure is induced from 0 to 50 GPa. Disordered Ag and Bi atoms have a large impact on band gap energy; in this case, the indirect band gap is transferred towards a direct band gap. We have seen that pressure-driven samples have transformed a band energy semiconductor into a metallic one. Under the induced hydrostatic pressure, the covalent bond is transformed into a metallic bond and the bond lengths are reduced. Meanwhile, pressure-induced samples enhance symmetry breaking in [AgBr6]5− and [BiBr6]3− octahedra, which reduces the density of states of the Fermi surface and lowers the total energy. The mechanical behaviors demonstrated that the studied materials are mechanically stable as well as ductile and their ductile nature is enhanced by the driving pressure. The absorption peak is shifted towards the low energy region with increased hydrostatic pressure. The absorptivity and dielectric constant values are also increased with driving pressure. Phase transformed double halide perovskites triggered by outside stimuli produce several outstanding materials properties, giving great scope for a broad range of applications. This type of pristine and disordered double halide perovskite with pressure-driven semiconductor-to-metal phase transition samples may have potential applications in optoelectronic and photovoltaic devices.
Highlights
In recent years, lead-free double halide perovskites have been considered promising candidates for versatile applications in low-cost photovoltaic and optoelectronic devices because of their unique electronic and optical properties.[1,2,3,4,5] Practical applications of inorganic halide perovskites have increased to a large scale, such as a light emitting diodes (LEDs), lasers, radiation detectors, and solar cells
We used the simulations of pristine and disordered Cs2AgBiBr6 in 4 Â 4 Â 4 gamma-centered (G) k-points. 5s2 5p6 6s1 for Cs, 4d10 5s1 for Ag, 6s2 6p3 for Bi, and 4s2 4p5 for Br were some of the valence band electronic con gurations used in these partial density of states (PDOS) calculations
The simulated structural parameters a and V decreased with an increase in hydrostatic pressure in pristine Cs2AgBiBr6 samples due to the space of lattice vacancies being reduced
Summary
Lead-free double halide perovskites have been considered promising candidates for versatile applications in low-cost photovoltaic and optoelectronic devices because of their unique electronic and optical properties.[1,2,3,4,5] Practical applications of inorganic halide perovskites have increased to a large scale, such as a light emitting diodes (LEDs), lasers, radiation detectors, and solar cells. Pb-based hybrid halide perovskites have superior and exceptional photovoltaic properties due to their suitable direct band gap, high absorption coefficients, effective masses of valence electrons and holes, defect tolerance, and carrier diffusion length.[6,7,8] In spite of breakthroughs, Pb based hybrid halides will have no use in the long term, because of their toxic impact on the environment.[9] There is a great challenge for a materials scientist to nd out the stable nature of a non-toxic double metal halide for low-cost optoelectronic device applications beyond all these restrictions.
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