Abstract
With an interest to quest for transition metal-based halogenated double perovskites AB′B″X6 as high performance semiconducting materials for optoelectronics, this study theoretically examined the electronic structures, stability, electronic (density of states and band structures), transport (effective masses of charge carriers), and optical properties (dielectric function and absorption coefficients, etc.) of the series A2AgCrBr6 (A = K, Rb, Cs) using SCAN + rVV10. Our results showed that A2AgCrBr6 (A = Rb, Cs), but not K2AgCrBr6, has a stable perovskite structure, which was revealed using various traditionally recommended geometry-based indices. Despite this reservation, all the three systems were shown to have similar band structures, density of states, and carrier effective masses of conducting holes and electrons, as well as the nature of the real and imaginary parts of their dielectric function, absorption coefficient, refractive index, and photoconductivity spectra. The small changes observed in any specific property of the series A2AgCrBr6 were due to the changes in the lattice properties driven by alkali substitution at the A site. A comparison with the corresponding properties of Cs2AgCrX6 (X = Cl, I) suggested that halogen substitution at the X-site can not only significantly shift the position of the onset of optical absorption found of the dielectric function, absorption coefficient and refractive spectra of Cs2AgCrCl6 and Cs2AgCrI6 toward the high- and low-energy infrared regions, respectively; but that it is also responsible in modifying their stability, electronic, transport, and optical absorption preferences. The large value of the high frequency dielectric constants—together with the appreciable magnitude of absorption coefficients and refractive indices, small values of effective masses of conducting electrons and holes, and the indirect nature of the bandgap transitions, among others—suggested that cubic A2AgCrBr6 (A = Rb, Cs) and Cs2AgCrCl6 may likely be a set of optoelectronic materials for subsequent experimental characterizations.
Highlights
Innovative materials that display impressive geometrical, stability, electronic, transport, and optical characteristics in the infrared through visible to ultraviolet region of the electromagnetic spectrum are a special class of semiconductors for application in optoelectronic devices [1,2,3,4,5,6,7,8,9]
Halide based single [10,11,12,13,14,15,16,17] and double perovskites [1,2,3,4,5,6,7,8,9,18,19,20,21,22] known by the chemical formulae ABX3 and AB B”X6, respectively, are examples of such compounds
In halide double perovskites with AB B”X6 composition [1,2,3,4,5,6,7,8,9,18,19,20,21,22,23,24], the B site is usually occupied with a monovalent transition metal or an alkali metal (e.g., Cu+, Ag+, and Na+) and the B” site is occupied with a transition metal or non-transition metal cation in the +3 oxidation state (e.g., Cr3+, In3+, Sb3+, Bi3+)
Summary
Innovative materials that display impressive geometrical, stability, electronic, transport, and optical characteristics in the infrared through visible to ultraviolet region of the electromagnetic spectrum are a special class of semiconductors for application in optoelectronic devices [1,2,3,4,5,6,7,8,9]. Halide based single [10,11,12,13,14,15,16,17] and double perovskites [1,2,3,4,5,6,7,8,9,18,19,20,21,22] known by the chemical formulae ABX3 and AB B”X6, respectively, are examples of such compounds Do they absorb light, but many of them emit light in specific regions of the electromagnetic spectrum, depending on the nature of ingredients at the atomic scale with which they are built.
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