Pyro-phototronic nanogenerator based on flexible 2D ZnO/graphene heterojunction and its application in self-powered Near Infrared photodetector and active analog frequency modulation

Even though 2D ZnO has been utilized for enhanced self-powered sensing by strain modulation due to its piezoelectric property, study on utilizing pyroelectric property of ZnO remains unexplored. The piezoelectric property of 2D ZnO works on mechanical strain which disrupts the structure of ZnO leading to the failure of device. For pyroelectric nanogenerator, temperature difference can be triggered by external light source which does not disrupt the ZnO structure and also avoids the need for physical bending/pressing as in case of piezoelectric nanogenerator. This work represents the first demonstration of fabrication of flexible 2D ZnO/Gr pyro-phototronic diode where the pyro potential generated in the 2D ZnO due to the NIR illumination adds/subtract with the built-in electric field of the heterojunction and modulates the depletion region of the heterojunction thereby enabling bias free operation. Further, the variation in the depletion width of the heterojunction was utilized as a variable capacitor in frequency modulator, wherein, with increasing intensity, frequency of oscillations increased from 9.8 MHz to 10.42 MHz. The work presented provides an alternative approach for self-powered NIR photodetector and to utilize the same at circuit level having potential applications in the fields of optothermal detections, electronic tuning circuits et