Optical inspection system with tunable exposure unit for micro-crack detection in solar wafers

Ko, Shun-Sheng; Liu, Chien-Sheng; Lin, Yang-Cheng

doi:10.1016/j.ijleo.2012.12.024

Cited by 30 publications

(17 citation statements)

References 11 publications

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“…Another technique involves the use of an LED light source (940 nm) with CCD camera to inspect and mark the position of microcracks in polycrystalline silicon wafers [60], [61]. Here, a tunable exposing system enabled the detection of microcracks even with inconstant thicknesses of the multicrystalline silicon wafer.…”

Section: A Optical Transmissionmentioning

confidence: 99%

Review of Microcrack Detection Techniques for Silicon Solar Cells

Abdelhamid

Singh

Omar

2014

IEEE J. Photovoltaics

112

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Microcracks at the device level in bulk solar cells are the current subject of substantial research by the photovoltaic (PV) industry. This review paper addresses nondestructive testing techniques that are used to detect microfacial and subfacial cracks. In this paper, we mainly focused on mono-and polycrystalline silicon PV devices and the root causes of the cracks in solar cells are described. We have categorized these cracks based on size and location in the wafer. The impact of the microcracks on electrical and mechanical performance of silicon solar cells is reviewed. For the first time, we have used the multi-attribute decision-making method to evaluate the different inspection tools that are available on the market. The decision-making tool is based on the analytical hierarchy process and our approach enables the ranking of the inspection tools for PV production stages, which have conflicting objectives and multi-attribute constraints.

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Section: A Optical Transmissionmentioning

confidence: 99%

Review of Microcrack Detection Techniques for Silicon Solar Cells

Abdelhamid

Singh

Omar

2014

IEEE J. Photovoltaics

112

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“…The LED light bar consists of high powered NIR LEDs with peak wavelengths at 940 nm. This specific wavelength was chosen due to its excellent ratio of light penetration and signal acquisition [5].…”

Section: B Proposed Imaging Systemmentioning

confidence: 99%

“…However, their method may not be suitable for a high-speed inline inspection as it requires a stepping mode type of conveyor system with varying stoppage time due to the inconsistent camera exposure, which may result in lengthy wafer transfer time. The proposed method by [5] is also not capable of handling solar wafers which contain varying thickness in different parts of the same wafer.…”

Section: Introductionmentioning

confidence: 97%

“…Reference [5] proposed a method which uses a photo diode to measure the transmission of the NIR light and adjusting the exposure of the camera to compensate for the wafer thickness. They have shown that by varying the exposure of the camera, they're able to successfully detect micro-cracks from previously low contrast images of wafers with variable thickness when the camera is set with a constant exposure.…”

Section: Introductionmentioning

confidence: 99%

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High-speed micro-crack detection of solar wafers with variable thickness

Teo

Mahdavipour

Abdullah

2014

2014 IEEE International Conference on Imaging Systems and Techniques (IST) Proceedings

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A new approach for high-speed micro-crack detection of solar wafers with variable thickness is proposed. Using a pair of laser displacement sensors, wafer thickness is measured and the lighting intensity is automatically adjusted to compensate for loss in NIR transmission due to varying thickness. In this way, the image contrast is maintained relatively uniform for the entire size of a wafer. An improved version of Niblack segmentation algorithm is developed for this application. Experimental results show the effectiveness of the system when tested with solar wafers with thickness ranging from 125 to 170 µm. Since the inspection is performed on the fly, therefore, a high throughput rate of more than 3600 wafers per hour can easily be obtained. Hence, the proposed system enables rapid in-line monitoring and real-time measurement.

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“…There are several stages related to the generation of microcracks [1][2][3][4][5][6][7][8]: (i) the cutting process of an ingot or crystal bar due to a local uneven force; (ii) the cell or module fabrication process due to external factors; (iii) improper module installation; and (iv) the power plant operation period due to external factors such as wind or ground subsidence. Since the microcracked silicon wafer is not completely broken apart, microcracks can be detected only through the electroluminescence (EL) test [9].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Microcrack Length in Silicon Cells on the Potential Induced Degradation Behavior

Gou

Wang

et al. 2018

International Journal of Photoenergy

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The presence of microcracks may lead to loss in the module output power and safety hazard of the module. This paper investigated whether the existed microscopic microcracks in cells will facilitate the PID behavior. Cells with different degrees of microcracks were fabricated into small modules to undergo the simulated PID test. The I-V performance and EL images of the modules were characterized before and after the PID test. The obtained results demonstrate that with the increase in the microcracked area or length, the modules would show a more serious PID behavior. The mechanism of this microcrack length-related degradation under high negative bias was proposed.

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Optical inspection system with tunable exposure unit for micro-crack detection in solar wafers

Cited by 30 publications

References 11 publications

Review of Microcrack Detection Techniques for Silicon Solar Cells

Review of Microcrack Detection Techniques for Silicon Solar Cells

High-speed micro-crack detection of solar wafers with variable thickness

The Effect of Microcrack Length in Silicon Cells on the Potential Induced Degradation Behavior

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