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Surface Roughness and Features of a Solar Cell

Importance of Solar Panel Testing

Maximizing a solar cell’s energy absorption is key for the technology’s survival as a renewable resource. The multiple layers of coating and glass protection allow for the absorption, transmittance, and reflection of light that is necessary for the photovoltaic cells to function. Given that most consumer solar cells operate at 15-18% efficiency, optimizing their energy output is an ongoing battle.

Studies have shown that surface roughness plays a pivotal role in the reflectance of light. The initial layer of glass must be as smooth as possible to mitigate reflectance of light, but the subsequent layers do not follow this guideline. A degree of roughness is necessary at each coatings interface to another to increase the possibility of light scattering within their respective depletion zones and increase the absorption of light within the cell1. Optimizing the surface roughness in these regions allows the solar cell to operate to the best of its ability and with the Nanovea HS2000 High Speed Sensor, measuring surface roughness can be done quickly and accurately.


Measurement Objective

In this study we will display the capabilities of the Nanovea HS2000 High Speed Sensor by measuring the surface roughness and geometric features of a photovoltaic cell. For this demonstration a monocrystalline solar cell with no glass protection will be measured but the methodology can be used for various other applications.



Test Procedure and Procedures

The following test parameters were used to measure the surface of the solar cell.



Results and Discussion

Depicted below is the 2D false-color view of the solar cell and an area extraction of the surface with its respective height parameters. A Gaussian filter was applied to both surfaces and a more aggressive index was used to flatten the extracted area. This excludes form (or waviness) larger than the cut-off index, leaving behind features that represent the solar cell’s roughness.







A profile was taken perpendicular to the orientation of the gridlines to measure their geometric characteristics which is shown below. The gridline width, step height, and pitch can be measured for any specific location on the solar cell.







Conclusion




In this study we were able to display the Nanovea HS2000 Line Sensor’s ability to measure a monocrystalline photovoltaic cell’s surface roughness and features. With the ability to automate accurate measurements of multiple samples and set pass fail limits, the Nanovea HS2000 Line Sensor is a perfect choice for quality control inspections.

Reference

1 Scholtz, Lubomir. Ladanyi, Libor. Mullerova, Jarmila. “Influence of Surface Roughness on Optical Characteristics of Multilayer Solar Cells “ Advances in Electrical and Electronic Engineering, vol. 12, no. 6, 2014, pp. 631-638.

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