The excellent device performance of lead-based perovskite is attributed to its remarkable optical and electronic properties. This series of solar-cell absorber materials has greatly improved the energy conversion efficiency from approximately 3.8% initially to more than 25%. Despite the rapid development of lead-based perovskites, the toxicity of lead atoms and their instability under heat, light, and humidity hinder the practical application of this type of perovskite photovoltaic technology. Therefore, it is very important to develop lead-free, non-toxic, and eco-friendly halide perovskites to replace lead-based materials in practical applications. The research on lead-free halide perovskites is one of the current study frontiers. This review summarizes the application of lead-free double perovskite Cs₂AgBiBr₆ in perovskite solar cells, introduces the structure and material preparation methods of Cs₂AgBiBr₆, discusses the device performance of perovskite solar cells, analyzes relevant strategies to improve the performance of this type of photovoltaic device, and discusses the challenges and development directions of lead-free perovskites.