Remarkably enhanced piezoelectric and ferroelectric characteristics of Er:ZnO upon graphene addition for wearable self-powered piezoelectric sensors

Abstract

Flexible Er-ZnO/PDMS and Er-GO/ZnO/PDMS nanogenerators with high energy harvesting performance were developed. The output voltage and current density of Er-doped ZnO, Er-doped GO/ZnO (1:10) and Er-doped GO/ZnO (1:5) nanocomposites-based piezoelectric harvesters were (70 V, 1.85 µAcm−2), (80 V, 2.16 µAcm−2) and (100 V, 2.47 µAcm−2), respectively. The Er-doped GO/ZnO wearable sensor showed output voltages of 4 V and 9 V by bending the human wrist and elbow, respectively. In addition, a remarkable improvement of the remnant polarization (Pr) and a favourable reduction of the coercive field (Ec) were achieved for Er-doped ZnO and Er-doped GO/ZnO nanocomposites. The corresponding values of Pr and Ec for pure ZnO, Er-doped ZnO, Er-doped GO/ZnO (1:10) and Er-doped GO/ZnO (1:5) nanostructures were (0.06 μC/cm2, 6.50 kV/cm), (8.75 μC/cm2, 4.74 kV/cm), (13.25 μC/cm2, 3.98 kV/cm) and (8.913 μC/cm2, 3.54 kV/cm), respectively. The enhanced piezoelectric and ferroelectric properties of Er-doped ZnO and Er-doped GO/ZnO nanocomposites make them futuristic hybrids with immense potential for designing pressure biosensors, mechanical energy harvesters and environmentally friendly ferroelectric-based memory devices.