Dual‐Source Evaporation Processed Novel NaBiS 2 Absorber Material for Eco‐Friendly and Stable Photovoltaics

Abstract Exploring and developing novel, low‐cost, and environmentally friendly photovoltaic materials is a vital trend in the evolution of solar cell technology. The distinctive properties of alkali bismuth ternary sulfides have spurred increased research and application in optoelectronic devices. In this study, a novel method is reported for preparing NaBiS 2 film by sequential thermal evaporation of Na 2 S and Bi 2 S 3 layers followed by heating post‐treatment for the first time, as well as the preparation of solar cells with NaBiS 2 as the light‐absorbing layer. Based on X‐ray diffraction and Raman analysis, the prepared NaBiS 2 film is confirmed to be a single‐phase material, without the presence of any secondary phases. Additionally, the photoelectric characteristics of NaBiS 2 are investigated and incorporated this material into solar cell devices. By optimizing the device architecture, the solar cell utilizing NaBiS 2 as the light‐absorbing layer achieved a photoelectric conversion efficiency of 2.91%, which is the highest efficiency reported for NaBiS 2 solar cells up to now. The research has provided a valuable perspective and path for the development of novel photovoltaic materials in the solar cell field.