Investigation of the structural stability, electronic properties, and thermoelectric performance of graphene enhanced (BA)₂SnI₄ two-dimensional halide perovskite for advanced thermoelectric applications

The toxicity of lead and instability remain primary obstacles limiting the widespread application of perovskite materials. Two-dimensional (2D) perovskites have demonstrated significantly improved stability compared to their three-dimensional (3D) counterparts due to enhanced hydrophobicity and resistance to degradation. However, studies investigating the thermoelectric potential of 2D perovskites remain limited, underscoring the need for a deeper understanding of their behavior and scalability for electronic and thermoelectric applications. In this study, density functional theory (DFT) is employed to investigate the structural stability, electronic properties, and thermoelectric performance of graphene-enhanced 2D (BA)₂SnI₄ perovskites. Graphene is of particular interest due to its large surface area, flexibility, transparency, and high charge-carrier mobility. Our results indicate that pristine (BA)₂SnI₄ exhibit semiconducting characteristics with well-defined band gap, making it suitable as a light-absorbing layer in optoelectronic devices. It also exhibits excellent thermoelectric performance, with a high Seebeck coefficient, peak power factor of 1.6 × 10⁻² W·m⁻¹·K⁻², and maximum figure of merit (ZT) of 3.5 at 100 K, making it ideal for low-temperature thermoelectric applications. Moreover, incorporating graphene improves electrical conductivity and stabilizes the power factor at 200–800 K, increases thermal conductivity while lowering the Seebeck coefficient and ZT to < 0.3. These results reveal an offset between stability and thermoelectric efficiency, pristine (BA)₂SnI₄ is optimal for low-temperature thermoelectrics, whereas graphene-modified systems, despite having lower ZT, are promising for moderate-to-high temperature applications wherein enhanced conductivity and thermal stability are crucial.