Although strain engineering has been extensively recognized as a critical pathway in controlling the properties of inorganic materials, there have been very limited reports on the external strain-dependent modulation of piezoelectricity in flexible systems. Herein, we introduce a technical way of imposing extra stress during the deposition of the ZnO nanorods by using the stretching mode of a polymer substrate, specifically for the purpose of enhancing piezoelectricity and bending-driven energy harvesting performance. Depending on the level of stretching up to 4.87% strain, the induced stress of the nanorod structure was modulated after the substrate-releasing step. The 4.87%-stretching mode resulted in an effective piezoelectric coefficient of 33.3 p.m./V corresponding to an enhancement by ~270% compared to the unstrained case. The resultant piezoelectric energy harvester demonstrated ~3.43 V output voltage and ~226 nA output current for the 4.87%-strained sample, which means respective increments by ~90% and ~85% with the application of in-situ strain. The origin of the improvements is chased by estimating the changes in lattice constants and spontaneous polarization, which are dependent on the level of in-situ strain.
Bibliographical noteFunding Information:
This work was financially supported by grants from the National Research Foundation of Korea ( NRF-2016M3A7B4910151 ); the Industrial Strategic Technology Development Program ( #10079981 ) and the Korea Institute of Energy Technology Evaluation and Planning Program (No. 20173010013340 ) funded by the Ministry of Trade, Industry, & Energy of Korea ; and the Creative Materials Discovery Program by the Ministry of Science and ICT of Korea ( 2018M3D1A1058536 ).
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)
- Electrical and Electronic Engineering