article · Physica Scripta
This research evaluates the structural, optoelectronic, and thermoelectric characteristics of potassium tin halide vacancy-ordered double perovskites in their stable monoclinic phase using density functional theory. The investigated compounds, K2SnCl6 and K2SnBr6, feature direct band gaps, whereas K2SnI6 demonstrates an indirect band gap. Optical band gap assessments place K2SnBr6 at 1.707 eV, K2SnCl6 at 2.581 eV, and K2SnI6 at 4.126 eV, supporting their utility as light absorbers. Evaluations of dielectric functions, absorption coefficients, and refractive indices further underline their photovoltaic capabilities. Additionally, the materials exhibit favourable thermoelectric performance derived from their thermal conductivities, Seebeck coefficients, and power factors. At a temperature of 500 K, maximum thermoelectric figure of merit values reach 0.58 for the chloride, 0.69 for the bromide, and 0.50 for the iodide compound.
Identifying stable, non-toxic, and efficient materials is crucial for the transition to cleaner energy systems. These findings reveal that potassium tin halide double perovskites possess suitable properties for both capturing solar energy and harvesting waste heat into electricity at elevated temperatures, expanding the pool of candidates for dual energy-conversion technologies.
The findings identify candidate materials for developers of photovoltaic cells and thermoelectric energy harvesters operating around 500 K. As this work is based purely on computational first-principles calculations, the research represents an early stage of development, requiring experimental synthesis and physical device testing before commercial implementation can be considered.
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Abstract The present study explores the structural, optoelectronic, and thermoelectric properties of potassium tin halide vacancy-ordered double perovskites K 2 SnX 6 (X = Cl, Br, and I) in their stable monoclinic phase. Our study uses first-principles calculations based on density functional theory (DFT). Electronic band structures reveal direct band gaps for K 2 SnCl 6 and K 2 SnBr 6 , while K 2 SnI 6 exhibits an indirect band gap. Theoretical computations utilising the modified Becke-Johnson potential (mBJ-GGA) demonstrate that the optical band gaps of K 2 SnCl 6 , K 2 SnBr 6 , and K 2 SnI 6 decrease in the following order: 2.581 eV, 1.707 eV, and 4.126 eV, respectively. These values render the materials suitable for photovoltaic applications. Analysis of dielectric functions, absorption coefficients, and refractive indices demonstrates their potential as light-absorbing materials. We evaluate the thermoelectric properties, including electronic and lattice thermal conductivities, Seebeck coefficients, and power factors, which lead to favorable thermoelectric performance. The maximum figure of merit (ZT) values of 0.58, 0.69, and 0.50 are achieved for K 2 SnCl 6 , K 2 SnBr 6 , and K 2 SnI 6 , respectively, at 500 K. These findings highlight the potential of these materials for applications in solar cells and thermoelectric devices, emphasising their effectiveness at elevated temperatures.
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DOI: 10.1088/1402-4896/ad1ad8
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