Alloying and Defect Control within Chalcogenide Perovskites for Optimized Photovoltaic Application

Abstract

Through density functional theory calculations, we show that the alloy perovskite system BaZr_1–<i>x</i>Ti_<i>x</i>S₃ (<i>x</i> < 0.25) is a promising candidate for producing high power conversion efficiency (PCE) solar cells with ultrathin absorber layers. To maximize the minority carrier lifetime, which is important for achieving high PCE, the defect calculations show that BaZr_1–<i>x</i>Ti_<i>x</i>S₃ films should be synthesized under moderate (i.e., near stoichiometric) growth conditions to minimize the formation of deep-level defects. The perovskite BaZrS₃ is also found to exhibit ambipolar self-doping properties, indicating the ability to form homo p–n junctions. However, our theoretical calculations and experimental solid-state reaction efforts indicate that the doped perovskite BaZr_1–<i>x</i>Ti_<i>x</i>S₃ (<i>x</i> > 0) may not be stable under thermal equilibrium growth conditions. Calculations of decomposition energies suggest that introducing compressive strain may be a plausible approach to stabilize BaZr_1–<i>x</i>Ti_<i>x</i>S₃ thin films