Polyaniline-based Schottky-triboelectric hybrid DC generators with tunable electrical outputs

Schottky direct-current (DC) generators can convert ambient mechanical energy into DC power, showing potential in portable electronics, wireless networks, and the Internet of Things. However, most Schottky DC generators generate a voltage output below 1 volt. Increasing the voltage output would considerably broaden their applications but remains challenging to achieve. In this study, we developed a novel DC generator that shows increased and tunable voltage outputs by combing the Schottky DC generator with triboelectric components. Using polyaniline-coated fabric and metal aluminum to prepare Schottky DC devices, we showed that the device voltage outputs were increased largely when a scatting layer of polyvinylidene fluoride (PVDF) powder covered the surface of either the metal Al or the polyaniline-coated fabric between them. Under compression impact, the PVDF-involved device (areal coverage 46.26 ± 0.60% on the Al surface) generated a peak open-circuit voltage of 3.2 ± 0.10 V and a short-circuit current of 15.06 ± 0.3 μA (current density 3.77 ± 0.08 μA cm−2), with a power of 12.32 ± 0.45 μW (measured by an external resistor method). The open-circuit voltage and power were 3.7 times and 1.5 times higher when compared with the same DC generator without PVDF. By changing the PVDF powder coverage area, the DC output voltage can be tuned linearly in the range of 0.86–3.20 V. However, when the coverage was above 50%, the outputs turned from DC to AC. We also simulated the electrical outputs using a circuit simulation program (LTspice XVII). The simulation results agreed well with the experimental findings, suggesting the improvement of the electrical output follows the classic electrical principle. Such Schottky diode-triboelectric hybrid may form a novel approach for developing DC energy harvesters and self-powered sensors with adjustable voltage output for various applications.