Resonance ultrasonic vibrations for crack detection in photovoltaic silicon wafers

Abstract

The resonance ultrasonic vibrations (RUV) technique is adapted for non-destructive crack detection in full-size silicon wafers for solar cells. The RUV methodology relies on deviation of the frequency response curve of a wafer, ultrasonically stimulated via vacuum coupled piezoelectric transducer, with a periphery crack versus regular non-cracked wafers as detected by a periphery mounted acoustic probe. Crack detection is illustrated on a set of cast wafers. We performed vibration mode identification on square-shaped production-grade Si wafers and confirmed by finite element analyses. The modelling was accomplished for the different modes of the resonance vibrations of a wafer with a periphery crack to assess the sensitivity of the RUV method relative to crack length and crack location.

Early degradation of silicon PV modules and guaranty conditions

“…In order to detect cracks and micro-cracks (u-cracks) in cells, a technique based on the analysis of the ultrasonic vibrations that follow an excitation can be used (Dallas et al, 2007;Monastyrskyi et al, 2008). This technique detects deviations in the characteristic frequency of the response after an ultrasonic excitation of the wafer.…”

“…The thickness has decreased from 300 um to less than 200 um, or sometimes even less than 100 um. Besides the decrease of cell thickness, the area of solar cells has increased to 210 mm x 210 mm (Dallas et al, 2007). This reduction of thickness and increase in area make the cells more fragile and susceptible to fractures during their manipulation, module lamination and storage.…”

Review of Microcrack Detection Techniques for Silicon Solar Cells

“…A typical RUV system can detect cracks up to submillimeter lengths. Dallas et al [68] used finite-element analysis modeling to select proper vibration mode to optimize the crack detection and increase the sensitivity of the RUV technique.…”

Fault diagnosis of photovoltaic modules through image processing and Canny edge detection on field thermographic measurements

“…Ideally, defective cells or cell strings are identified and rejected during the early stages of a module's manufacturing process, using, e.g. ultrasonic methods (Dallas, Polupan, and Ostapenko 2007), thermal flux thermography (Breitenstein et al 2005;Gupta and Breitenstein 2007;Krenzinger and de Andrade 2007;Van der Borg and Burgers 2003) or EL imaging (Fuyuky et al 2005;Kasemann et al 2006). However, even if this is performed in a coherent and effective manner, new defects may occur either within the stage of string/module assembling or during the lifetime of an operating module.…”