Silver sulfide thin film solar cells: materials, fabrication methods, devices, and challenges

Abstract

Photovoltaic (PV) technology provides a sustainable solution to meet the increasing energy demands from society. Silver sulfide (Ag₂S), a direct bandgap PV material, is considered a promising semiconductor due to its excellent optical and electrical properties, including high theoretical efficiency (∼30%), tunable bandgap (E_g = 0.9–1.1 eV), high thermodynamic stability, low toxicity, abundant elemental availability, and low fabrication cost. Despite efforts to improve the photovoltaic conversion efficiency of Ag₂S devices through various approaches such as film deposition techniques, device structures, and interface optimization, the quality of the absorber layer, structural defects, and non-ideal charge separation at the interfaces remain obstacles for further performance enhancement. Therefore, it is crucial to gain a deeper understanding of the fabrication methods, optoelectronic properties, and efficiency loss mechanisms of Ag₂S solar cells to achieve rapid advancements in device performance. This review summarizes the current research status on the fabrication methods, device structure selection, design, and optimization of Ag₂S thin films. Finally, insights into achieving high-efficiency Ag₂S devices by improving the crystallinity of the absorber layer and reducing interface defects are discussed.