AWARDSSHORTLIST
PV MATERIALS ENABLING AWARD
One piece AZO cylindrical sputter target
Thin film photovoltaic solar cells rely heavily on well controlled deposition processes (mainly PVD and CVD) for realizing each of the layers in the stack design. Independently of the thin film technology being used, the formation of a high quality TCO (transparent conductive oxide) layer is essential and AZO (Aluminum doped Zinc Oxide) has been the preferred material for use in thin film Si and CIGS solar cells.
Sputtering the layer from a ceramic target on a heated substrate (between 200 and 250 °C) has proven to realize layers with the best optical and electrical properties.
Furthermore, sputtering from cylindrical ceramic targets on rotatable magnetrons is being accepted as the way to go for achieving the lowest cost-of- ownership while sustaining a stable deposition process for long production cycles. State-of-the-art cylindrical AZO targets consist of sintered rings that are bonded on a stainless steel backing tube. The bonding process is often cumbersome and involves the use of expensive low melting point materials.
Cu-Ga Rotary Targets
Cu-Ga rotary targets provide the material used in a sputtering system, for deposition on thin-film solar cell substrates. The copper and gallium are deposited in a single sputtering step to the substrate – which will later combine with indium and selenium/sulfur to for the CIGS active layer.
The product addresses the inherent segregation issues of a casted target. This segregation results in a large grain size and sputtered film that may be somewhat non-homogeneous.
The product solves the problem of an alloy segregation as it is built from a powder metal that has undergone a high thermal cooling rate that keeps the material very homogeneous. The result is a target that is very homogeneous throughout. What is particularly noteworthy, Indium are the first company to develop and produce, in mass
The present invention breaks with this tradition by offering a single piece AZO cylindrical target which can be up to 4 meter long. In addition, the newly presented AZO target has the material directly applied onto the backing tube, ensuring a better contact and allowing higher power levels. A single piece product also avoids the risks of sputter process instabilities (e.g. arcing) that may occur at grooves which are present in between adjacent material segments. Moreover, the potential variation in material quality of combining various ring segments on the same target tube is completely overcome by having one single sold AZO piece.
PV MATERIALS ENABLING AWARD
production, a rotary Cu-Ga target. Customers benefit from this innovation in a couple different ways. In a technical sense, customers benefit from more homogeneous Cu-Ga sputtering targets than are otherwise available by the casting method.
This translates into more consistent and uniform coatings on thin-film cells.
A second benefit may not be as obvious: in-depth technical support throughout the material selection process, through the use of the targets. In this way, offering more than just the target material.
PV MATERIALS ENABLING AWARD
33
Philips Research
Substrate Conformal Imprint Lithography: large area direct nano- patterning of silica for ultimate light trapping.
Philips Research have developed a novel soft-stamp based wafer scale liquid embossing technique with nano-meter resolution. They call it Substrate Conformal Imprint Lithography, or SCIL. They used designer nano-imprinted patterns to increase the light absorption in thin-film a-Si:H solar cells where our patterns have up to 8% better performance compared to random light trapping structures.
Designer nano-patterns are increasingly studied to be used for light management
www.solar-pv-management.com Issue V 2010
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