La simulation ab initio pour l’investigation des matériaux semiconducteurs ferroélectriques pour des applications photovoltaïques

Abstract

Achieving high power conversion efficiencies (PCEs) in ferroelectric photovoltaics (PVs) is a challenging task. Recent studies have shown that ferroelectric oxide perovskites can achieve PCEs of over 1%, but they still suffer from severe recombination due to their large bandgap. To improve PCEs, reducing the bandgap may be necessary, even if it results in a loss of light absorption. Halide perovskites have a narrow bandgap and high absorption coefficient, making them a promising material for solar cells. In this study, we investigate the structural, optoelectronic, and ferroelectric properties of ABX3 halide perovskite materials, including CsGeCl3, CsGeBr3, CsGeI3, and BaTiO3, using firstprinciples density functional theory (DFT) and the modern theory of polarization based on the Berry phase approach. We also evaluate their photovoltaic performance using the Spectroscopic Limited Maximum Efficiency (SLME) model. Our results show that the considered perovskites are semiconductors with a direct energy band gap and high absorption coefficients, making them promising materials for solar cells and other optoelectronic devices. The ferroelectric polarization creates a potential gradient that supports electron-hole separation, leading to a spectroscopic limited maximum efficiency of 28%. We also find that polar CsGeI3 exhibits a large shift current bulk photovoltaic effect in the visible region, making it the best ferroelectric Pb-free inorganic metal halide semiconductor for solar cell applications. Finally, we investigate the ferroelectric properties of (AA’)(BB’)I6 double perovskite superlattices, including (CsRb)(SnGe)I6, (CsK)(SnGe)I6, and (RbK)(SnGe)I6, and find that they host hybridimproper ferroelectricity despite the tilting pattern of the I octahedra in bulk (AA’)(BB’)I6. The magnitude of the ferroelectricity is comparable to that of conventional ferroelectric materials. In addition, the electronic and optical properties of these double perovskite superlattices were investigated using the same methodology. The results suggest that these materials possess a direct band gap and high absorption coefficient, making them an excellent candidate for use in photovoltaic and optoelectronic applications. Their superior electronic and optical properties, combined with environmentally friendly and non-toxic nature, make them a promising material for future sustainable energy devices. Overall, the findings of this study contribute to a deeper understanding of the structureproperty relationships in perovskite materials, and provide insights into the design of new materials with improved performance. It is anticipated that these results will pave the way for the development of Pb-free, non-toxic and sustainable optoelectronic devices.