This study highlights K2Tl(As/Sb)I6 as a thermodynamically stable, lead-free double perovskite with exceptional bifunctional photovoltaic and thermoelectric performance, making it a promising candidate for next-generation clean energy applications. We have explored the structural, optoelectronic and thermoelectric properties by using DFT while their photovoltaic properties have been explored with the help of SCAPS-1D simulations. The predicted negative formation energy and the lower fluctuation in RMSD obtained through DFT calculations, indicates that K2Tl(As/Sb)I6 is thermodynamically stable. Furthermore, electronic property analysis using the TB-mBJ method reveals that both K2TlAsI6 and K2TlSbI6 possess a desirable direct band gap of 1.16 eV and 1.04 eV, respectively—ideal for optoelectronic applications. The optical analyses unveil remarkable absorption coefficients, soaring to the impressive magnitude of 10⁵ cm⁻¹, beyond the threshold energy of 1.18 eV for K2TlAsI6 and 1.05 eV for K2TlSbI6. These compounds exhibit notable electrical conductivity and minimal reflectivity, attributed to their well-dispersed band structures and optimally aligned band gap values. The thermoelectric evaluation highlights exceptional ZT values of 0.79 and 0.74 at 510 K for K2TlSbI6 and K2TlAsI6, respectively, owing to their ultra-low thermal conductivity (κₑ/τ ~ 1014 W m−1−1 s−1) and remarkably high electrical conductivity (σ/τ ~ 1019 Ω m−1 s−1) over a wide temperature range of 200–650 K. Furthermore, SCAPS-1D simulations unveil outstanding photovoltaic performance, showcasing peak power conversion efficiencies of 30.01% (31.77%) for Ag/Cu2O/K2TlAsI6/TiO2/FTO (Ag/Cu2O/K2TlSbI6/TiO2/FTO), with corresponding JSC values of 40.69 mA/cm2 (45.07 mA/cm2), VOC of 0.93 V (0.81 V), and fill factors of 84.07% (82.21%). These remarkable figures surpass those of recently reported lead-free halide double perovskite solar cells, driven by the excellent electronic and optical characteristics of K2Tl(As/Sb)I6. This study provides a promising pathway toward the realization of next-generation high-efficiency solar cells and thermoelectric devices based on eco-friendly materials.

Exploration of the Structural, Optoelectronic, Thermoelectric, and Photovoltaic Characteristics of K₂Tl(As/Sb)I₆ via DFT and SCAPS-1D Simulations

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发表日期：

2025年5月9日

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Mukaddar Sk,
M. T. Islam,
Deepshikha Burman

摘要

This study highlights K₂Tl(As/Sb)I₆ as a thermodynamically stable, lead-free double perovskite with exceptional bifunctional photovoltaic and thermoelectric performance, making it a promising candidate for next-generation clean energy applications. We have explored the structural, optoelectronic and thermoelectric properties by using DFT while their photovoltaic properties have been explored with the help of SCAPS-1D simulations. The predicted negative formation energy and the lower fluctuation in RMSD obtained through DFT calculations, indicates that K₂Tl(As/Sb)I₆ is thermodynamically stable. Furthermore, electronic property analysis using the TB-mBJ method reveals that both K₂TlAsI₆ and K₂TlSbI₆ possess a desirable direct band gap of 1.16 eV and 1.04 eV, respectively—ideal for optoelectronic applications. The optical analyses unveil remarkable absorption coefficients, soaring to the impressive magnitude of 10⁵ cm⁻¹, beyond the threshold energy of 1.18 eV for K₂TlAsI₆ and 1.05 eV for K₂TlSbI₆. These compounds exhibit notable electrical conductivity and minimal reflectivity, attributed to their well-dispersed band structures and optimally aligned band gap values. The thermoelectric evaluation highlights exceptional ZT values of 0.79 and 0.74 at 510 K for K₂TlSbI₆ and K₂TlAsI₆, respectively, owing to their ultra-low thermal conductivity (κₑ/τ ~ 10¹⁴ W m⁻¹⁻¹ s⁻¹) and remarkably high electrical conductivity (σ/τ ~ 10¹⁹ Ω m⁻¹ s⁻¹) over a wide temperature range of 200–650 K. Furthermore, SCAPS-1D simulations unveil outstanding photovoltaic performance, showcasing peak power conversion efficiencies of 30.01% (31.77%) for Ag/Cu₂O/K₂TlAsI₆/TiO₂/FTO (Ag/Cu₂O/K₂TlSbI₆/TiO₂/FTO), with corresponding J_SC values of 40.69 mA/cm² (45.07 mA/cm²), V_OC of 0.93 V (0.81 V), and fill factors of 84.07% (82.21%). These remarkable figures surpass those of recently reported lead-free halide double perovskite solar cells, driven by the excellent electronic and optical characteristics of K₂Tl(As/Sb)I₆. This study provides a promising pathway toward the realization of next-generation high-efficiency solar cells and thermoelectric devices based on eco-friendly materials.

Exploration of the Structural, Optoelectronic, Thermoelectric, and Photovoltaic Characteristics of K2Tl(As/Sb)I6 via DFT and SCAPS-1D Simulations

摘要

Exploration of the Structural, Optoelectronic, Thermoelectric, and Photovoltaic Characteristics of K₂Tl(As/Sb)I₆ via DFT and SCAPS-1D Simulations