A major efficiency boost in photovoltaics

TRUMPF lasers and HÜTTINGER generators expand solar cell production opportunities

Press Release

Solar cell


Ditzingen, Germany, September 05, 2011 - The photovoltaic industry is currently faced with a challenge, namely, to produce solar cells with an increasingly higher degree of efficiency while also reducing processing costs and establishing ever more efficient production processes. At the 26th European Photovoltaic Solar Energy Conference (EUPVSEC), TRUMPF and HÜTTINGER Elektronik will present micro-processing lasers from the TruMicro series and generators from the TruPlasma series. These are innovative products that are opening up new production opportunities for solar cell manufacturers and facility construction companies.

The laser as an industrial tool is a key technology in the photovoltaics industry. In comparison to alternate processes, it is considerably more efficient. It increases production flow rates and simultaneously reduces production costs.

Lasers for thin-film solar cell processing
In the production of solar modules from amorphous silicon (aSi) or cadmium telluride (CdTe), conductive and photoactive films are deposited on large substrate areas, such as glass. After every deposition, the laser subdivides the surface in such a way that the cells created are automatically switched in series by the process sequence. In this way, cell and module tensions, depending on the cell width, can be set. The transparent conductive oxides (TCO) are usually processed with lasers of infrared wavelength. At typical feed rates, repetition rates of over 100 kilohertz are achieved. An optimized pulse to pulse overlap makes for a clean kerf and minimizes short circuits. Small, compact instruments such as lasers from the TRUMPF TruMicro Series 3000 with wavelengths of 1064 and 532 nm are ideal for P1, P2, and P3 patterning. With their high pulse-to-pulse stability, the diode-pumped solid-state lasers do not just achieve very good processing results, they can also be easily integrated into existing systems because of their advanced cooling design.

The patterning of thin-film cells made of Cu(In,Ga)(S,Se)2, also known as CI(G)S, presents a particularly high challenge for the laser process. This is true for structuring of molybdenum, too. For this application, nanosecond lasers are still used, but far better solutions exist, such as picosecond lasers. With these lasers, the material is ablated with ultrashort pulses without significant heating of the process edge zone, which prevents cracking, melting or exfoliation of the layers.

TRUMPF offers powerful picosecond lasers from the TruMicro Series 5000 with a wavelength of 1030 nm for structuring of molybdenum and 515 nm for processing photoactive material and patterning the front contact. In addition, TRUMPF's TruMicro Series 5000 are picosecond lasers with up to 100 watts of output power which illustrate the best operation cost per watt.

Solar cell

Edge deletion: Lasers replace sandblasting
To protect thin-film solar modules against unfavorable environmental influences, especially moisture, a width of approximately 10 millimeters of the layer system is ablated along the edge and covered with a laminated film. For the most part, the photovoltaic industry still uses sandblasting for this purpose. However, lasers are far more suitable for this process. The tool of choice for this application is the TruMicro 7050, which can process large areas at production speed reliably and securely. It generates pulses with a duration of 30 nanoseconds at an average power of 750 watts.

Crystalline solar cells: Lasers reduce the per watt costs
Future laser applications include the selective ablation of passivated layers on crystalline solar cells. Here, lasers with ultrashort pulses and high pulse energies are particularly well-suited, due to the excellent beam quality. These conditions can be achieved only by means of disk laser technology at this time. Because of the simple scalability of the laser output, a higher production capacity can be achieved, and the high beam quality in the ultrashort pulses significantly improves solar cell efficiency. All of this will result in significantly reducing the per watt costs of solar cell performance in the future.

Power supplies - core for the deposition of thin film solar cells
The production of thin layer solar cells involves using photoactive semiconductors to extensively coat the glass substrate. A simple but cardinal rule in this process is: The better the quality of the deposited layers, the higher the efficiency of the finished solar cell. The requirements for the power supplies that deliver the necessary power for the coating process are therefore clear: They have to produce thin and homogenous layers while maintaining efficient production. For the two main production steps, the PECVD (plasma-supported chemical vapor deposition) and sputtering processes, HÜTTINGER provides generators that fulfill these requirements to a high level.

TruPlasma RF Series 1000 for stable PECVD processes
Especially designed for PECVD processes that solar manufacturers use for ablating silicon-based coatings, the TruPlasma RF Series 1000 from HÜTTINGER is the perfect solution. This family of innovative high-frequency generators was technologically improved and enhanced in spring 2011.

Currently available as part of the TruPlasma RF Series 1000, is the high-frequency TruPlasma RF 1003 generator. At a frequency of 13.56 megahertz, it produces output power of three kilowatts and delivers the necessary energy for coating and etching in the production of solar cells with a high degree of precision and reproducibility. To carry out these processes using less power, HÜTTINGER has now improved this product family. With the TruPlasma RF 1001 and the TruMicro RF 1002, power supplies with one and two kilowatt outputs are now available. These generators help keep facility expenses down because they cost less to purchase and operate.

HÜTTINGER has also equipped the new and improved TruPlasma RF Series 1000 with an extra communications interface. As an alternative to the previous RS232/485 interface, the process power supply now also comes with a PROFIBUS connection. This means that the generators can now operate optimally on the European market. As a result of the new interface and its very compact size, the power supplies can be integrated into the machines easily and economically.

In addition, HÜTTINGER has also considerably improved output power stability. To make it more measurable and controllable, the company has implemented a higher signal processing resolution in the machine's control system. This means more accurate recordings of the output power generated in the power supply are possible and the precise results reported back to the control systems. The output power can be reliably and precisely adjusted at any time and adapted to the target value. Stable processes and optimal process results are the result.

Sputtering made easy with new DC power supplies
HÜTTINGER has developed the TruPlasma DC Series 3000 NEW for sputtering processes which solar manufacturers use to deposit TCO such as aluminum-doped zinc oxides (AZO) or indium tin oxide (ITO). Available with outputs of 2 to 160 kilowatts, these direct current generators facilitate thin and homogenous layers, even in high-arcing processes like TCO sputtering.

Yet what makes the TruPlasma DC Series 3000 NEW so special? Mainly it's the system's innovative arc management system CompensateLine, which HÜTTINGER has once again improved. If an arc occurs, CompensateLine balances the stored energy in the output circuit as well as in the connection cable between the generator and the cathode even more efficiently. This results in a very fast generator response time on the arc and keeps residual energy to a minimum. It enables the production of high quality TCO films with significantly higher deposition rates than of those with a pulsed DC power supply. High deposition rates increase the productivity of the TCO process. In addition, the cost of the power supply is reduced. The continuous DC power supply functions well without the expensive, high-power switching stages that are necessary for pulsed DC power supplies. With increased productivity and reduced investment cost, the TruPlasma DC Series 3000 NEW pays off twice for the user.

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