Innovative metallization process for reliable, high-efficiency solar cells

September 24, 2012, IMEC

Imec today announced that it has developed an innovative process for plated front contact formation of silicon solar cells using only one sequence to plate several metals. The large-area solar cells were processed in imec's labs and combine an excellent reliability with a conversion efficiency of 20.3% (certified at Fraunhofer ISE-Callab). The full plating sequence has been transferred to an in-line plating tool enabling high throughput.

The new process for plated contact formation uses one plating sequence (plating Ni, Cu, and Ag), followed by a thermal anneal. This single sequence plating process results in a better aspect ratio and minimal silver usage compared to the standard screen-printed metallization with silver paste. The improved aspect ratio reduces the shadow loss and thus increases the , while the metallization with mainly copper provides a more sustainable alternative to the currently used silver metallization.

The resulting of the plated contacts is excellent as solder tab adhesion pull tests show a pull strength beyond 2N. Produced with this process, single-cell laminates and mini-modules have successfully passed one and a half times the thermal cycling and damp heat cycles defined by IEC 61215, the industry's standard which qualifies and modules for long-term operation.

Dr. Jef Poortmans, director Photovoltaics research at imec: "This new metallization process is the latest optimization to imec's PERC process, optimizing the cost-of-ownership and conversion of cells through structure and material optimizations. The process and resulting large-area Cz p-type are fully compatible with the requirements of industrial photovoltaic production. With a certified efficiency of 20.3% and a recent batch of cells with even higher efficiencies, next steps in our R&D should boost efficiencies of PERC solar cells to well over 21%."

The results were achieved within imec's silicon solar cell industrial affiliation program (IIAP), a multi-partner R&D program that explores and develops advanced process technologies aiming a sharp reduction in silicon use, whilst increasing cell efficiency and hence further lowering substantially the cost per Watt peak. Industrial partners that wish to integrate innovative processes into their solar cell production are welcome to join imec's R&D program.

Explore further: IMEC presents large area solar cells with 18.4% conversion efficiency, featuring Cu-plated contacts

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not rated yet Sep 24, 2012
Why doesn't anyone develop water cooled solar cells?

It seems simple enough, you don't even need micro-channels though that is conceivable.

Dan Rojas on Greenpowerscience proved that a fully submerged solar panel is 10% more efficient (or about 1% more of total thermodynamic efficiency vs an ideal machine,) even though water should block some of the light.

This is caused by reducing the heat of the panel and thereby increasing it's thermodynamic efficiency.

This worked for several reasons.

1, water is a better conductor of heat than is air, with a higher heat capacity.

2, The water and the aquarium blocked the less useful IR, preventing much of the heat from ever hitting the panel in the first place.

3, the heat is quickly distributed throughout the much larger volume of the water, in his experiment.

With a well developed design, the water used to cool the panels could be later fed into a direct solar heater for use inside.

10% improvement from a low-tech passive system.
not rated yet Sep 24, 2012
Why don't they ever mention an estimated market price?

Why not put a thermoelectric layer on the back side, with water cooling on the back surface of the thermoelectric layer so that you can leach off the waste heat, converting it to electricity, and all the while increasing the efficiency of the solar cell by keeping it cooler?

I mean damn, why don't people with p.h.d. think of this stuff?

That should be able to get you up to around another 10 to 15% of an ideal machine, or about 30 to 35% total efficiency.

I'm not a dumbass, but why not?!
not rated yet Sep 24, 2012
Why doesn't anyone develop water cooled solar cells?

Because if you had bothered to google you might have noticed that they've been on the market for quite some time.

Why not put a thermoelectric layer on the back side,

Because currently they're too expensive for such low temperature differential applications. If a cell is a luxury item that will never recoup its cost then it won't sell.

I mean damn, why don't people with p.h.d. think of this stuff?

Because this is R&D - not Hollywood magic. Researchers work on one aspect. that's tasking enough. Putting a system together from that which is cheap and easy to manufacture is an engineering problem (which comes MUCH later)

I'm not a dumbass,

Yes you are - because you confuse research with engineering with production with marketing.

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