Novel Ag-based thin film solar cells: concept, materials, and challenges

Novel Ag-based thin film solar cells have attracted extensive attention in recent years in the photovoltaic (PV) field due to their outstanding properties like a high light absorption coefficient, low toxicity, abundance, and an appropriate band gap. The emerging Ag-based thin film materials such as Ag2S, AgBiS2, Ag3CuS2, AgInS2, AgBiSe2, Ag2ZnSnS4, Ag(In1-x,Ga-x)Se-2, AgaBibIc, Cs2AgBiBr6, and Cu2AgBiI6 are becoming ideal materials for light absorbing layers in the new generation of PV devices. Although the efficiency of ATFSCs has improved significantly in recent years, it is much lower than those of other PV devices. The relatively low efficiency of ATFSCs is mainly caused by structural defects such as poor crystallinity, voids, and instability which occur during the preparation of light absorbing layers. This paper defines the concept and classification of Ag-based materials and introduces in detail a thin film preparation method by overcoming structural defects. Finally, the vision of achieving high-efficiency ATFSCs by improving structural defects is proposed.