A. Subramani, C. Senthil, J. Luxa, S. Mourdikoudis, S. David, Z. Sofer
University of Chemistry and Technology,
Czech Republic
Keywords: perovskite solar cells, hole transport layers, chalcogenide, density functional theory
Summary:
Perovskite solar cells (PSCs) have demonstrated remarkable power conversion efficiencies (PCEs) exceeding 25%, making them competitive with traditional silicon solar cells [1]. However, their stability and charge transport limitations hinder commercialization. One of the primary challenges lies in the instability of hole transport layers (HTLs), necessitating the development of cost-effective and efficient alternatives[2]. In this study, density functional theory (DFT) calculations were performed to investigate the electronic, optical, and dielectric properties of two ternary chalcogenide compounds—AgInP₂Se₆ and AgInP₂S₆—as potential transport layers in PSCs. Our results reveal that AgInP₂Se₆ has a band gap ~0.925 eV, while AgInP₂S₆ exhibits a band gap ~1.044 eV at high symmetry point. Mulliken population analysis indicates stronger charge localization in AgInP₂S₆, enhancing its suitability as an HTL. Born effective charge analysis shows that AgInP₂Se₆ exhibits greater Born effective charges, particularly in diagonal elements, indicating enhanced coupling between atomic displacements and polarization. Additionally, AgInP₂Se₆ demonstrates higher polarizability along the zzz-axis, suggesting greater anisotropic dielectric and optical behavior. The reduced dielectric response and lower polarizability of AgInP₂S₆ contribute to its efficiency as an HTL by facilitating hole mobility while minimizing electron transport. To validate the theoretical findings, we successfully synthesized AgInP₂S₆ and AgInP₂Se₆ experimentally and characterized them using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD analysis confirms the crystalline phase purity of the synthesized materials, while SEM imaging provides insights into their surface morphology. These experimental results further reinforce the suitability of AgInP₂S₆ as a stable and effective HTL, in PSCs. The combined computational and experimental insights from this study contribute to the advancement of scalable and stable PSC technologies through the integration of novel chalcogenide-based transport materials.