Simulation study on the performance of wide band gap quaternary compound Cu₂BaSnS₄ for indoor solar cells in IoT applications

Abstract Indoor photovoltaic (IPV) cells are designed to operate under low-intensity artificial light sources. Generally, artificial light sources have a narrow spectrum, which can be efficiently captured by a wide band gap absorber. However, existing wide band gap absorbers, such as amorphous silicon (a-Si), perovskite (MAPbX 3 ), suffer from toxicity and stability issues, making it essential to explore an alternative that is an earth-abundant, environmentally friendly. In this study, we used Vienna ab initio Simulation Package (VASP)-based ab-initio calculations to investigate Cu 2 BaSnS 4 (CBTS) materials, focusing on their crystal structure, optoelectronic properties, and performed SCAPS-based simulations for performance estimation. CBTS exhibits a direct band gap ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>E</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>g</mml:mi> </mml:mrow> </mml:msub> </mml:math> ) of ∼1.9 eV and high absorption coefficient ( α ∼ 10 5 cm −1 ) in the UV-visible spectrum, making it ideal for IPV applications. Detailed balance calculations predict remarkable solar cell efficiencies of 59.96% ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>E</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>g</mml:mi> </mml:mrow> </mml:msub> </mml:math> = 1.9 eV) and 57.51% ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>E</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>g</mml:mi> </mml:mrow> </mml:msub> </mml:math> = 1.95 eV) under indoor light emitting diode (LED) and compact fluorescent light (CFL) lighting. The simulated efficiency exceeding 50% are attributed to the narrow emission spectrum of indoor light sources, which is efficiently absorbed by wide band gap CBTS. Key factors influencing efficiency include high shunt resistance (R Sh &gt; 10 6 Ω cm 2 ) and minimal impact of series resistance up to 100 Ω cm 2 . A key distinction between IPV and outdoor photovoltaics is the lower photo-generated carrier concentration in low-light conditions, leading to a higher ratio of trapped to photo-generated carriers. These findings highlight CBTS’s potential for next-generation indoor energy solutions.