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Efficiency of PV installations requires quality-tuned production processes

Contributed Paper supporting PV CellTech 2018

Process stability and manufacturing quality benefit from inline quality control and direct process feedback

Solar business is driven by clean energy policies and air pollution concerns worldwide. Accordingly, the global PV industry will continue its growth well into the future.

In order to meet growing demand and competition, manufacturers will have to continue reducing production costs and cycle times, while simultaneously increasing product quality.

High level AOI in cell tester/sorter is the first step

In future, we will see even more growth in PV market. At the same time, quality standards within the PV business are simultaneously increasing: but there is still a lot to be done.

In some PV markets, quality control is currently applied only at the very end of production lines, by inspection in cell testers and sorters. Most commonly, automated optical inspection (AOI) systems are installed besides the IV-tester (flasher) to additionally sort cells into different color classes.

Some systems also sort into different optical quality levels, and some even inspect the rear side of cells. Often these systems are not ideal, or properly parametrized, to do perform the task adequately. Often, sorting levels are set to only partially satisfy module producers’ requirements.

VITRONIC supplies with the VINSPEC SOLAR state-of-the-art AOI systems which can bring about significant improvements. These systems are applied for sorting into color classes, as well detecting corner and edge breakages, surface defects and doing accurate inspection with high pixel resolution.

These sophisticated systems have two main advantages.

First, these modern solutions offer human-like color classification. Second, high performance inspection helps to reject cells that could later cause degradation: e.g. cells with bad firing, bad metallization, print interruptions, uneven coatings, improper laser openings, missing rear side print, as well as residues from chemicals.

Quality must be produced and not sorted

Powerful quality inspection in cell testing and sorting is essential.

However, in order to achieve the highest cell efficiency - and to guarantee future quality requirements - high performance optical inline inspection (directly after each surface and metallization process) is mandatory.

Significant improvements in yield and quality distribution by AOI after every step of production

Optical inspection along the entire cell production line enables stable processes and high cell quality with a narrow tolerance range (see figure1).

Figure 1: Optimized coating and metallization processes lead to optimized quality distribution.

Early detection of errors, by implemented trend analyses and evaluations from heatmaps, avoids quality deviations.

Industry 4.0 features, such as data correlation within and between production equipment, enables an ongoing optimization of the production process. This not only avoids error, but also increases productivity, especially when short feedback loops are installed.

VITRONICS’ post-print inspection can be used as an example here.

Early detection of screen wear with VINSPEC SOLAR extends screen lifetime (3,000 to 8,000 additional prints) and reduces downtime (up to 10%), because corrective action can be taken immediately (using fast feedback).

Figure 2: Optimized print parameters reduce average finger width with a reduction in silver paste required.

Another example is the optimization of print parameters using the optical inspection data (see figure 2). Adherence to strict quality limits reduces average finger width which guarantees optimum efficiency in the installation. In addition, this saves 1% to 3% in silver paste, reducing production costs.

Therefore, the use of high performance image processing makes an important contribution to efficient cell production processes, and helps to avoid degradation in PV plants.



VITRONIC is a leading supplier of high performance machine vision solutions. The owner-managed group of companies, founded in 1984, develops innovative products and customized solutions in the growth industries of industrial and logistics automation and traffic technology. In photovoltaics VITRONIC looks back to more than 10 years of experience. Manufacturers of solar cells and modules around the world look to VITRONIC for automated optical inspection systems (AOI) that give them a competitive edge. And with more than 2,000 successful PV installations for over 80 customers worldwide, the track record speaks for itself. In 2015, the VITRONIC group generated total revenue of over 110 million euros.

VITRONIC is a Supporting Partner of PV CellTech 2018 in Penang, Malaysia, 13-14 March 2018.