GaN/Al2O3 core-shell nanowire based flexible and stable piezoelectric energy harvester

Abstract Flexible and stable piezoelectric energy harvesters (PEHs) were fabricated based on polydimethylsiloxane-embedded m-axis GaN/Al2O3 core-shell nanowires (NWs) transferred to indium (In)-deposited flexible substrates. The piezoelectric performance was optimized by controlling the Al2O3 shell thickness on GaN NWs. The huge barrier height of Al2O3 suppresses the junction current screening effect, and the remnant piezopotential in the GaN region at the GaN-Al2O3 interface modulates the transportation of carriers. Because of the significant suppression of the junction current screening and reduction in the leakage current, the PEHs could effectively harvest mechanical energy, even from static strain. The PEH based on core-shell NWs with a controlled Al2O3 thickness of 6 nm exhibited the maximum piezoelectric performance. Reduced piezoelectric performance was observed by increasing and decreasing the thickness of the Al2O3 shell from 6 nm. For higher thickness, the performance was reduced because of the significant voltage drop across the GaN-Al2O3 interface. However, for lower thickness the performance was reduced due to the direct tunneling of the current from the GaN-Al2O3 interface. The optimized PEH also worked as an energy supplier to demonstrate the light emitting diode operation.