Cerium-based lead-free chalcogenide perovskites for photovoltaics

Inorganic-organic hybrid lead halide perovskites have shown great prospects in solar cells in recent years, and their power conversion efficiency (PCE) has reached up to $25.5%$. However, Pb toxicity and poor ambient stability have remained two unsolved urgent problems. To address these problems, more and more researchers have begun to focus on the application of inorganic lead-free perovskites in the photovoltaic field. Herein, several cerium-based lead-free inorganic chalcogenide perovskites $A{\mathrm{CeTe}}_{3}$ $(A=\mathrm{Ca},\mathrm{Sr},\mathrm{Ba})$ are proposed as suitable optical absorbers for thin-film solar cells based on first-principles calculations. The distorted-phase $A{\mathrm{CeTe}}_{3}$ perovskites are predicted as direct-band-gap semiconductors with a gap value of 1.02--1.13 eV. Moreover, the distorted $A{\mathrm{CeTe}}_{3}$ not only possess a strong optical absorption coefficient $({10}^{5}--{10}^{6}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1})$, superior to ${\mathrm{MAPbI}}_{3} ({\mathrm{MA}}^{+}={\mathrm{CH}}_{3}{\mathrm{NH}}_{3}^{+})$, but also have excellent PCE, especially for ${\mathrm{BaCeTe}}_{3}$, whose PCE can reach $\ensuremath{\sim}29%$ even in a thin film $(1\ensuremath{\mu}\mathrm{m})$. All these characteristics render distorted $A{\mathrm{CeTe}}_{3}$ perovskites promising photovoltaic materials.