Synergistic Band Engineering and Ferroelectric Polarization in Sn/S Co-doped BaTiO3 for Integrated Photovoltaic-Energy Storage

Abstract

This study innovatively proposes an approach to directly store the energy generated by the photovoltaic effect within the material itself by leveraging its inherent energy storage properties. A functional integrated material with outstanding energy storage and photovoltaic performance has been designed. In recent years, perovskite ferroelectric materials have exhibited considerable potential for applications in integrated photovoltaic energy storage (PV-ES) systems, attributable to their distinctive crystal structures and inherent spontaneous polarization properties. Nevertheless, the conventional perovskite ferroelectric material BaTiO3 (BTO) is limited by its wide bandgap, which results in inadequate visible light absorption, as well as by its relatively low spontaneous polarization (Ps) and elevated leakage current. These limitations impede significant advancements in energy storage density and efficiency, thereby constraining its widespread utilization in photovoltaic and energy storage domains. In response to these challenges, this study for the first time systematically investigated the electronic structure, optical properties, photovoltaic characteristics, and ferroelectric properties of Sn/S co-doped BTO (BTSOS) through first-principles calculations, revealing its promising potential applications in the field of integrated PV-ES. The findings reveal the thermodynamic stability of BTSOS, as evidenced by a formation energy of -6.194 eV. Mechanically, BTSOS demonstrates stability with an increased bulk modulus relative to BTO, while exhibiting reduced shear and Young’s modulus, indicative of enhanced compressive strength coupled with improved flexibility. Bandgap calculations employing both the PBE and HSE06 hybrid functionals yield values of 1.552 eV and 2.783 eV for BTSOS, respectively, representing a substantial reduction compared to pristine BTO. This bandgap narrowing corresponds to an elevated absorption coefficient within the visible spectrum, thereby facilitating more efficient light harvesting. Additionally, BTSOS displays an increased static dielectric constant. Finally, the BTSOS exhibited a short-circuit current density (Jsc) of 468.843 A/m², the maximum power density (Pmax) of 271.477 W/m², and the photoelectric conversion efficiency (PCE) of 27.138%. Moreover, the Ps of BTO is 0.294 C/m², and its energy barrier (ΔE) is 20.105 meV. In comparison, the Ps of BTSOS is significantly increased to 0.337 C/m², and the ΔE rises to 63.801 meV. In summary, BTSOS demonstrates simultaneous optimization of both photovoltaic and energy storage performance, positioning it as a promising candidate material for integrated PV-ES systems. This advancement offers novel insights for the design of highly efficient and stable PV-ES systems and provides a valuable theoretical foundation for the development and commercialization of next-generation solar PV-ES technologies.