Machine learning-assisted lead-free CsCu₂I₃/ZnO heterojunction for high response H₂S sensing

The CsCu 2 I 3 /ZnO-heterojunction-based sensor enables H 2 S detection with a response value of 0.83 at 1 ppm, with response and recovery times of 240 s and 834 s. • The CsCu 2 I 3 /ZnO heterojunction improves structural stability and ensures continuous and stable sensor response. • The CsCu 2 I 3 /ZnO-heterojunction-based sensor achieves self‐calibration for different H 2 S concentrations with 99% detection accuracy. Hydrogen sulfide (H 2 S), a colorless and toxic gas, poses serious health risks upon prolonged exposure, including damage to respiratory and cardiovascular systems, which can be fatal in severe cases. Current H 2 S sensors suffer from limited response, particularly in detecting ultra‐low concentrations. To overcome this limitation, we developed a CsCu 2 I 3 /ZnO heterojunction‐based gas sensor via vacuum evaporation. This composite material enables highly responsive H 2 S detection at room temperature. The heterojunction not only improves structural stability but also ensures continuous and stable sensor response. At 1 ppm H 2 S, the sensor exhibits a sensitivity of 0.72, the response value of 0.83, the limit of detection (LOD) of 14.25 ppb, with response and recovery times of 240 s and 834 s, respectively. Furthermore, an intelligent calibration framework was developed by integrating Gramian Angular Summation Fields with the AlexNet algorithm, operating as a robustness enhancer. The sensor achieves self‐calibration for different H 2 S concentrations with 99.33% detection accuracy through 5-Fold Cross-Validation, significantly enhancing quantification capability. These results demonstrate the excellent potential of our CsCu 2 I 3 /ZnO-heterojunction-based sensor in H 2 S monitoring. The combination of responsive materials with machine learning offers a robust strategy for advancing ultra‐low concentration gas detection technologies.