Abstract
Chalcogenide perovskites have shown great potential for photovoltaic applications. Most researchers have begun to pay close attention to the crystal synthesis, phase stability, and optoelectronic properties of chalcogenide perovskites AMX(3) (A = Ca, Sr, Ba; M = Ti, Zr, Hf, Sn; X = S, Se). At present, the A-site metal cations are mainly limited to alkaline earth metal cations in the literature. The replacement of the alkaline earth metal cations by Yb(2+) is proposed as an alternative for chalcogenide perovskites. In this study, the phase stability, and mechanical, electronic, optical, and photovoltaic properties of novel chalcogenides YbMX(3) (M = Zr, Hf; X = S, Se) are theoretically evaluated in detail for the first time. It is mentioned that YbZrS(3) and YbHfS(3) are marginally thermodynamically stable while YbZrSe(3) and YbHfSe(3) exhibit superior phase stability against decomposition. Good mechanical and dynamical stability of these chalcogenide perovskites are verified, and they are all ductile materials. The accurate electronic structure calculations suggest that the predicted direct bandgap of YbMSe(3) (M = Zr, Hf) is within 1.3-1.7 eV. Additionally, the small effective mass and low exciton binding energy of YbMSe(3) (M = Zr, Hf) are favorable for their photovoltaic applications. However, YbZrS(3) and YbHfS(3) show larger direct band gaps with a change from 1.92 to 2.27 eV. The optical and photovoltaic properties of these compounds are thoroughly studied. In accordance with their band gaps, YbZrSe(3) and YbHfSe(3) are discovered to exhibit high visible-light absorption coefficients. The maximum conversion efficiency analysis shows that YbMSe(3) (M = Zr, Hf) can achieve an excellent efficiency, especially for YbZrSe(3), whose efficiency can reach ~32% in a film thickness of 1 μm. Overall, our study uncovers that YbZrSe(3) is an ideal stable photovoltaic material with a high efficiency comparable to those of lead-based halide perovskites.