Vanadium‐Doped ZnO Nanorod Piezoelectric Nanogenerators for Self‐Powered NH 3 Gas Sensing With UV‐Modulated Response

ABSTRACT This work presents a high‐performance, self‐powered ammonia (NH 3 ) gas sensor based on vanadium‐doped ZnO (V:ZnO) nanorod arrays integrated into a piezoelectric nanogenerator (PENG). V:ZnO nanorods with doping concentrations from 0.25 to 1.00 mM were synthesized via a hydrothermal method. Structural, chemical, and optical characterizations indicate that vanadium incorporation modifies defect‐related states and surface oxygen species, thereby improving surface reactivity and piezotronic transduction. The optimized 0.75 mM V:ZnO PENG achieves a superior voltage response of 67.2% to 75 ppm NH 3 , nearly doubling the performance of pure ZnO (35.6%) under bias‐free operation. Under 254 nm UV illumination, the device exhibits a pronounced increase in baseline current, indicating UV‐induced carrier modulation rather than an independent UV‐sensing mode. Finite element analysis (FEA) further supports the role of gas‐induced surface charge variation in regulating the internal piezopotential distribution. This research provides a promising strategy for developing defect‐engineered, self‐powered NH 3 gas sensors based on piezoelectric semiconductor nanostructures.