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nanotimes Research

11-08 :: August 2011

Solar Cells II // Long-Term-Stable Copper Metallization and Industrially

Feasible Processes Have Enabled 21.4% Efficiency © Text: Fraunhofer ISE

R

eductions in the electricity generation costs for photovoltaics can be reached through two

mechanisms: improving the efficiency of solar cells and reducing their production costs. With advanced processes for metallization of solar cells, both effects can be reached at the same time. In the ETAlab®

at

Fraunhofer ISE, Germany, the technology of produ- cing solar cell contacts 100% from low-cost materials has been achieved. In doing so, industrially feasible galvanic processes were used and expensive silver has been replaced, mostly by copper. The resear- chers achieved a solar cell efficiency of 21.4% using this approach. Especially remarkable: this result is comparable with values from solar cells using a highly efficient titanium/palladium/silver contact system, which must be created in comparatively expensive vacuum laboratory processes.

An efficiency potential for solar cells is provided by the galvanic nickel-copper system with direct de- position to silicon, without a printed silver contact layer. Using an industrially feasible process, such as laser ablation, the anti-reflection coating (ARC) is removed locally. Structural widths in the range of 20µm are achieved, which significantly reduces shading in comparison to screen printing. In the affected areas of the ARC, nickel will be selectively deposited, which is then reinforced and made sol-

“Our copper-metallized solar cells from the ETAlab® are not only comparable with the efficiency of the titanium/palladium/silver reference technology, but also show an excellent stability in long-term tests. A thermal stress test of 1600 hours at 200° C (392° F) had no consequences for the efficiency,” says Jonas Bartsch, Team Leader “Plating Process Technology”.

With the process knowledge built up at Fraunhofer ISE, the researchers at the ETAlab®

are working on transferring this technology to large solar cell formats.

derable by the addition of copper and zinc or silver. On solar cells with front and rear side passivation in a 2x2 cm² format, this technology reached an effici- ency of 21.4% in ETAlab®

, which was confirmed by CalLab PV Cells at Fraunhofer ISE.

Contact: Fraunhofer Institute for Solar Energy Systems ISE, Jonas Bartsch, Phone: +49 (0) 7 61 / 45 88 - 55 61

Dr. Markus Glatthaar, Phone: +49 (0) 7 61 / 45 88 - 52 72 http://www.ise.fraunhofer.de