Cauliflower-like copper zinc tin sulfur for ppb-level NO2 sensing at room temperature

Structure nanocrystallization dramatically enhances the specific surface area and is one of the most popular methods for preparing high-performance gas sensing materials. However, most of the preparation methods are suffering high-cost and long time-consuming. This work synthesized Cu2ZnSnS4 (CZTS), a cost-effective and stable direct-bandgap semiconductor with cauliflower-like morphology by facile solution drop coating and low-temperature annealing. The morphology and gas sensing performance of CZTS films could be modulated by controlling the annealing time. The gas sensors showed a significant response toward ppb-level NO2 (1.287 toward 50 ppb) with a short response, recovery time, and high selectivity at room temperature (25 °C). It is worth mentioning that the limit of detection is 50 ppb, which is the first report on the ppb-level detection ability of CZTS-based NO2 gas sensors. The enhanced sensitivity of the cauliflower-like CZTS nanocrystal-based gas sensor can be ascribed to the small grain size, large specific surface area for effective gas diffusion, and excellent conductivity of the spherical packed structure.