Machine learning and first-principles study of non-lead-halogen Cs2NaB’Cl6 (B’= In, Cr, Y, Tb) double halide perovskites with optoelectronic properties

In the field of photovoltaic materials, wide-bandgap (Eg > 1.63 eV) perovskite solar cells have broad application prospects in the power generation of tandem solar cells and the integration of photovoltaics into buildings, with advantages such as a light absorption coefficient, long carrier lifetime, strong response to weak light, and a simple preparation process. In this paper, the relevant data obtained by machine learning are screened and combined with the development concept of high efficiency and environmental protection; the lead-free Cs₂NaB’Cl₆ (B’ = In, Cr, Y, and Tb double-halide perovskite) is selected as the research object from the perspective of bandgap and energy. The structure and optoelectronic properties of the system are investigated using the first-principles density functional theory method. In terms of electrical performance, Cs₂NaInCl₆ and Cs₂NaCrCl₆ can be used for wide-bandgap perovskite batteries because of their bandgaps of 2.81 and 2.86 eV, while Cs₂NaYCl₆ and Cs₂NaTbCl₆ have bandgaps of 5.05 and 5.19 eV, which can be used for detectors. In terms of optical performance, the reflectivity of Cs₂NaB’Cl₆ (B’ = In, Cr, Y, Tb)-halide perovskite is all less than 11 %, with low reflection loss and no metallic luster, so the material system has high transmittance and can be used for research and development of high-transmittance applications. CsNaCrCl₆ shows a significant absorption peak in the visible light range, and the three materials show a significant absorption peak in the ultraviolet region. It is found that Cs₂NaCrCl₆ has broad application prospects in the field of tandem solar photovoltaic power generation and photovoltaic building integration because of its appropriate bandgap value, low reflectivity, and excellent light absorption performance. Cs₂NaInCl₆, Cs₂NaYCl₆, and Cs₂NaTbCl₆ have low dielectric constants, high chemical stability, high exciton binding energy, and excellent electrical properties and can be used as wide-bandgap, direct-bandgap, halide double-perovskite semiconductor materials and have potential application value in optoelectronic devices and optical detectors.