Preparation Of ZnO Piezoelectric Thin Films And Study On Energy Harvesting And Sensing Characteristics

Zinc oxide(ZnO)is a semiconductor material with great potential for application.With its many characteristics being developed,it is possible to change people's lives and contribute to the sustainable development of human beings in the future.As an N-type semiconductor,ZnO has a wide band gap and a very high exciton binding energy.It has piezoelectric,optical and ultra-high stability.Particularly noteworthy is that as a member of piezoelectric materials,zinc oxide can be used to prepare devices that convert energy generated by pressure into electricity.The advantage of ZnO material is that the energy acquisition device can be directly used without polarization.It is non-toxic,green and environmentally friendly,and its price is low.In this paper,we use ZnO as a piezoelectric layer to fabricate a multi-layer vibration energy collector,which can detect the acceleration of the object.At the same time,a triangular ZnO-based energy harvester is proposed,which effectively improves the voltage output of the energy collector.A flexible transparent energy harvester with multi-layer structure is fabricated by using the optical and piezoelectric properties of ZnO and Al-doped zinc oxide(AZO)as transparent electrodes.It can be used as a self-powered sensor,which reflects the good application prospects of ZnO energy harvester in the field of self-powered tactile sensing.There are many methods to prepare ZnO.In this paper,electrochemical deposition and magnetron sputtering are used to prepare ZnO materials.Specific research contents and results are as follows:1.In the present study,ZnO energy harvester was fabricated on PET-ITO flexible substrates by electrochemical deposition.The ZnO nanorods were examined using an X-ray diffractometer,a scanning electron microscope,and an electrochemical workstation.The results show that the ZnO nanorods exhibit a preferred orientation of the(002)peak that varies with the deposition time.SEM images show that the ZnO nanorods that were electrodeposited in under 2 h exhibit a significant hexagonal wurtzite structure.SEM cross-sectional images of these ZnO nanorods show that they have a length of up to 1.1 ?m.To better observe the piezoelectric properties of energy harvester for which the ZnO nanorods were deposited over different durations,three different types of energy harvester were prepared.The results show that the energy harvester with the ZnO nanorods that were deposited in under 2 h has an output voltage of 960 mV.In addition,this paper explains the working mechanism of an energy harvester prepared using the electrodeposition method.2.A piezoelectric energy harvester with a thickness of about 80 ?m for miniaturized self-powered acceleration sensors is presented.In order to deposit piezoelectric zinc oxide(ZnO)thin film,a magnetron sputtering device was used.The polymethyl methacrylate(PMMA)and Aluminum-doped zinc oxide(AZO)are the insulating layer and the top electrode of the energy harvester,respectively.XRD results show that all annealed ZnO films have preferred orientation of[002]peak.The grain size of ZnO films is larger when the annealing temperature is 150?.It was found that the energy harvester with AZO/PMMA/ZnO/stainless steel structure has a higher output voltage.What's more,annealing temperature affects the value of the open circuit voltage of the energy harvester.The experiment shows that the output voltage reaches 3.81 V with the annealing temperature is 150?.The open-circuit voltage output voltage of the prepared self-powered accelerometer increases linearly with acceleration.And the small energy harvester-based accelerometer with excellent fatigue resistance can be used for acceleration measurement of small and lightweight devices.A triangular shaped piezoelectric vibration energy harvester(TS-PVEH)with zinc oxide(ZnO)thin films as the piezoelectric layer is reported.The effect of post-annealing temperature on the microstructure and piezoelectric performance of ZnO thin film deposited by the magnetron sputtering method is investigated firstly.Four prototypes of triangular energy harvester(TS-PVEH)with different structure parameters are fabricated and optimized.The simulation and experiment results indicate that the height and width of the triangular structure have a significant influence on the vibration mode and the output performance of TS-PVEHs.The optimization results indicate that the third prototype has the best output performance.Its open-circuit voltage and short-circuit current are 290 mV and 1.25?A,respectively,when the vibration acceleration is 5 m/s2 and the frequency is 56 Hz.Moreover,it has the highest load power density of 0.035 ?W/cm2 when the load is 0.1 M?.3.Transparent ZnO materials were prepared by magnetron sputtering on flexible and transparent polydimethylsiloxane(PDMS)materials as piezoelectric layers.A ZnO-based flexible transparent energy harvester having a seven-layer structure of PDMS/AZO/PDMS/ZnO/PDMS/AZO/PDMS was prepared for use as a self-powered sensor.The XRD results show that the ZnO piezoelectric films grown on PDMS layer have a good preferred orientation in[0002]direction.The transmission of the prepared sensors was analyzed in the visible light range by using UV-vis equipment.The results showed that the transmission rate was about 80%.The surface of the ZnO/PDMS structure was observed by SEM.It was found that ZnO was uniformly deposited on the surface of the PDMS substrate.The SEM observation of the section of the flexible transparent energy harvester showed that the thickness of ZnO was 550 nm.The sensor was tested for bending and found that the voltage first increased with the increase of the bending angle,and the voltage was maximum when the bending angle was 90 degrees.The pressure test of the sensor shows that the voltage output increases with the increase of the pressure in the test range.At the same time,the results of the vibration test show that the piezoelectric signal of the sensor increases with the increase of acceleration.Finally,the sensor is attached to the wrist,and the movement of the hand is well detected and a voltage signal of different characteristics is generated.