Design And Fabrication Of Air-based Line-focus Air-coupled Transducers And The Application On Detection Of Silicon Cell

In recent years,in order to deal with such problems as energy shortage and environmental pollution,solar energy has become the focus of the world.Besides,in the production process of monocrystalline silicon solar cells,it's inevitably to come across defects such as cracks,perforations and so on.The existence of these kinds of defects will seriously affect the photoelectric conversion efficiency of the solar cells and thus will increase the waste of materials and the costs of production.Aiming at the need of detection on monocrystalline silicon solar cells in photovoltaic industry,this research has carried out the design and fabrication of linefocus air-coupled transducers based on the air-based piezoelectric composites.In addition,non-contact detection experiments are implemented on monocrystalline solar cells with crack defects by air-coupled ultrasonic Lamb waves.The main contents include:(1)Based on the air-based piezoelectric composites and by use of PZFlex simulation software,the modeling of line-focus piezoelectric composites with single arc and double arcs are established,mean while their resonant characteristics and sound field characteristics are simulated analytically.The results show that the mechanical quality factor of these two air-based piezoelectric composites are smaller than that of PZT-5H,and the bandwidth of line-focus piezoelectric composite with single arc is wider than that of piezoelectric composite with double arcs.In addition,the acoustic field distribution of these two piezoelectric composites are focused compared with planar model.(2)According to the design parameters from the simulated calculation results,the PZT columns,epoxy brackets and metal electrodes are fabricated with the combination of fine cutting,3D printing and sputtering deposition.The resonant characteristics,acoustic impedance and the exciting and receiving characteristics of the manufactured piezoelectric composites are tested.The results show that the performance parameters of the actual piezoelectric composites are in accord with the simulated results.(3)Taking monocrystalline silicon solar cell as the experimental subject and using the air coupling ultrasonic testing system,the influence of the change of the ultrasonic wave's incident angle on Lamb waves in the monocrystalline silicon solar cells is studied here.According to the optimum angle of incidence,the monocrystalline silicon solar cells with perforative crack and non-perforative crack are scanned by means of correlation coefficients.The research results show that the air-coupled transducers have good applicability in detecting crack defects based on Lamb waves.