Abstract
ZnO nanowires are excellent candidates for energy harvesters, mechanical sensors, piezotronic and piezophototronic devices. The key parameters governing the general performance of the integrated devices include the dimensions of the ZnO nanowires used, their doping level, and surface trap density. However, although the method used to grow these nanowires has a strong impact on these parameters, its influence on the performance of the devices has been neither elucidated nor optimized yet. In this paper, we implement numerical simulations based on the finite element method combining the mechanical, piezoelectric, and semiconducting characteristic of the devices to reveal the influence of the growth method of ZnO nanowires. The electrical response of vertically integrated piezoelectric nanogenerators (VING) based on ZnO nanowire arrays operating in compression mode is investigated in detail. The properties of ZnO nanowires grown by the most widely used methods are taken into account on the basis of a thorough and comprehensive analysis of the experimental data found in the literature. Our results show that the performance of VING devices should be drastically affected by growth method. Important optimization guidelines are found. In particular, the optimal nanowire radius that would lead to best device performance is deduced for each growth method.
Highlights
With the rapid advancement in smart wearable systems and biomimetic robot technology, piezoelectric nanogenerators (PENGs) have received significant attention, for instance in the field of self-powered sensors [1] and artificial skin [2]
We theoretically explore the role of free charge carriers, surface traps, and NW dimensions on the output potential of piezoelectric nanocomposites based on ZnO NWs with account for the latitude of variation offered by growth methods
NWs grown by eachlevel method range of radius (R),the a typical length value, a typical range of doping (Nd ),using and astandtypical ard conditions, namely any intentional doping and post-deposition treatment: a surface trap density
Summary
With the rapid advancement in smart wearable systems and biomimetic robot technology, piezoelectric nanogenerators (PENGs) have received significant attention, for instance in the field of self-powered sensors [1] and artificial skin [2]. Several groups have worked on PENGs based on piezoelectric nanostructures with different configurations, in particular laterally integrated nanogenerators (LING) [5,6] and vertically integrated nanogenerators (VING) [6,7,8,9,10], this last one being the most commonly used configuration due to its easy manufacturing process and its high performance [11]. The VING configuration consists of an array of vertical NWs, grown on a flexible or rigid substrate and immerged into a dielectric matrix, contacted by bottom and top electrodes. The devices can be operated under bending [12,13,14] or compressive forces [6,7,8,9,10], the compressive mode being so far the most widely studied one.
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