Dual-Source Evaporation Processed Novel NaBiS₂ Absorber Material for Eco-Friendly and Stable Photovoltaics

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 NaBiS₂ film by sequential thermal evaporation of Na₂S and Bi₂S₃ layers followed by heating post-treatment for the first time, as well as the preparation of solar cells with NaBiS₂ as the light-absorbing layer. Based on X-ray diffraction and Raman analysis, the prepared NaBiS₂ film is confirmed to be a single-phase material, without the presence of any secondary phases. Additionally, the photoelectric characteristics of NaBiS₂ are investigated and incorporated this material into solar cell devices. By optimizing the device architecture, the solar cell utilizing NaBiS₂ as the light-absorbing layer achieved a photoelectric conversion efficiency of 2.91%, which is the highest efficiency reported for NaBiS₂ 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.