An ultra-sensitive humidity sensor based on lead-free halide perovskite Cs2TeI6 for real-time human breath and finger monitoring

•All-inorganic lead-free halide perovskite Cs2TeI6 was synthesized by a hydrothermal method.•Cs2TeI6 was explored as an impedimetric humidity sensing material for the first time.•Cs2TeI6 exhibited excellent humidity sensing properties.•Cs2TeI6 has great application potential in breath monitoring and finger detection.