Ga-doped ZnO nanowire nanogenerator as self-powered/active humidity sensor with high sensitivity and fast response

•Room-temperature self-powered/active humidity sensor is realized.•The device does not need external electric power.•Ga-doped ZnO nanowire arrays are synthesized via a very facile way.•The device has high sensitivity and fast response against humidity.•New piezo-humidity sensing mechanism with element doping is established.

High sensitivity and fast response piezo-humidity sensing have been realized from Ga-doped ZnO nanowire (NW) nanogenerator (NG) as self-powered/active gas sensor. The piezoelectric output generated by Ga-doped ZnO NW NG can not only act as a power source for driving the device, but also as a sensing signal for detecting humidity. Upon exposure to 80% relative humidity (RH) at room temperature, the piezoelectric output of Ga-doped ZnO NWs decreases from 0.56 V (in 45% RH) to 0.12 V, and the sensitivity is up to 358, higher than that of undoped ZnO NWs. In addition, the response time of Ga-doped ZnO NWs is 5 s, much shorter than that of undoped ZnO NWs. Such high performance can be ascribed to that Ga3+ ions can provide many donor defects and produce high local charge density/strong electrostatic field. The present results demonstrate a feasible approach for realizing high performance self-powered/active humidity sensor.

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