Enhanced output performance of flexible piezoelectric energy harvester by using auxetic graphene films as electrodes

We demonstrate an effective approach to enhance the output performance of a flexible piezoelectric energy harvester by using flexible electrodes with negative Poisson's ratio (NPR). The relationship between open-circuit voltage and Poisson's ratio of electrodes is established theoretically by deriving the analytical expression. It reveals a continuous increasing trend in open-circuit voltage with the decrease in Poisson's ratio of the electrodes. Further, graphene-assembled macro-film (GAMF), an NPR material with excellent flexibility and high conductivity, is used as the electrodes to fabricate flexible piezoelectric energy harvesters. Compared with the energy harvesters using silver electrode, the harvesters made by GAMF electrodes, with an NPR of -0.39, achieve nearly 1.7-times enhancement in open-circuit voltage and 1.6-times in short-circuit current for output performance. The experimental results are highly consistent with the simulation results, indicating that the GAMF has great prospects in developing flexible piezoelectric energy harvesters with enhanced electrical output performance.