The Structural, stability, electronic and optoelectronics properties of Y2AgBiX6 (Y = K, Na, li; X = I, Br, Cl) halide double Perovskites: A First-Principles study

Abstract

The crystal structure, electronic and optoelectronic properties of halide double perovskites Y₂AgBiX₆ (Y = K, Na, Li; X = I, Br, Cl) have been studied by first principles (FPs) in this paper. According to the elastic modulus and formation energy of crystal Li₂AgBiX₆, its structural stability is poor. In addition, the dependence of their electronic and mechanical properties, the effective mass of carriers and light absorption on elemental composition has been analyzed, and it is inferred that these materials have good electron transport properties. The photovoltaic characteristics of halide perovskite materials (PMs) based on potassium and sodium are studied. The photovoltaic properties of perovskite films with thickness of 1 μm, 5 μm and 10 μm were further analyzed, and it was found that the absorption was the highest when the film thickness was 10 μm. The current–voltage curve of the solar cell with above perovskite as absorbing material is calculated and analyzed by first principles. The result shows that Na₂AgBiBr₆, Na₂AgBiCl₆, K₂AgBiI₆ and K₂AgBiCl₆ are predicted to have excellent photovoltaic properties. Compared to other commonly used PMs, perovskite Y₂AgBiX₆ (Y = K, Na, Li; X = I, Br, Cl) has a smaller effective mass, which may contribute to good carrier transport and high performance of its optoelectronic devices. The absorption curves of K₂AgBiBr₆, K₂AgBiCl₆, Na₂AgBiBr₆, Li₂AgBiBr₆, and Li₂AgBiCl₆ matched well with the spectral irradiance of AM 1.5. Taken together, K₂AgBiBr₆ and Na₂AgBiBr₆ are the most suitable candidates for solar cell absorption layers because of their appropriate band gap and good stability.