Fraunhofer ISE Sets Another Solar Cell Efficiency Record

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Originally published on Sustainnovate.


A solar conversion efficiency of 25.1% has been achieved for the first time for a “both sides-contacted silicon solar cell,” by the Fraunhofer Institute for Solar Energy Systems ISE, a 2014 Zayed Future Energy Prize award winner.

The achievement marks the setting of a new world record for the solar cell type, and seems to signal great future potential for efficiency improvements as well.

For those not familiar with the cell type, both sides-contacted silicon solar cells are noted for featuring metal contacts on both the front and the rear of the cells. The new record-holding cells also utilized a full-area passivated back contact.

“To improve the solar cell efficiency, the focus has been on increasingly complex solar cell structures up to now,” stated Dr Martin Hermle, Head of the High Efficiency Solar Cells department at Fraunhofer ISE. “The biggest advantage of our new concept is that we can now contact the entire rear cell surface without patterning. Compared to the high-efficiency solar cell structures presently in use, we offer both a simplified manufacturing process and higher efficiencies at the same time.”


Some further details via a recent press release:

With the so-called TOPCon (Tunnel Oxide Passivated Contact) technology, developed by Fraunhofer ISE, metal contacts are applied to the rear side without patterning. To achieve this, the Fraunhofer researchers developed a selective passivated contact made of tunnel oxide that enables majority charge carriers to pass and prevents the minority carriers from recombining. The thickness of the intermediate passivation layer is reduced to one or two nanometers, allowing the charge carriers to “tunnel” through it. Subsequently, a thin coating of highly doped silicon is deposited over the entire layer of ultra-thin tunnel oxide. This novel combination of layers allows electrical current to flow out of the cell with nearly zero loss.

In the photovoltaics industry, the majority of solar cells have an aluminum-alloyed back contact covering the entire rear side. This type of contact, however, limits the efficiency. Therefore, the industry currently retrofits their production to incorporate the PERC (Passivated Emitter Rear Cell) technology in order to increase the solar cell efficiency. With PERC technology, only a small area on the rear side is contacted in order to reduce recombination. PERC, however, requires additional patterning steps and leads to longer current conduction paths in the silicon wafer. TOPCon, on the other hand, offers a possible approach to reduce these loss mechanisms and increase the efficiency.

“With TOPCon, we have developed a pioneering technology to increase the efficiency of silicon solar cells,” stated Professor Stefan Glunz, Division Director of Solar Cells – Development and Characterization. “At 25.1% efficiency, we are the first research institute to cross the 25% mark with an evolutionary further development for both sides-contacted solar cells and to close the gap on the world record efficiency for back contacted solar cells.”

The research team involved in the concept has reportedly been working on it for around 3 years now, with steady improvements to conversion efficiency being made via the approach.

Image ©Fraunhofer ISE

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14 thoughts on “Fraunhofer ISE Sets Another Solar Cell Efficiency Record

  • It’s gibberish, but really nice-warm-feeling gibberish. 25%! I suppose the underlying cell is mono. SunPower’s best (PERC?) mono cell is 24%, so it’s not a huge jump, but the process should be cheaper.

    • James, I’ve been reading cleantechica for only a couple months, but I enjoy reading your comments as much as the articles themselves. You seem to know quite a bit about the field. Thanks for taking the time to post.

      • James is a treasure.

        • You too Bob.

          • A tarnished one, at best….

            I have “impulse control” problems ;o)

          • lol. That’s what makes me think you may indeed be human. 😀

        • (blushes)

          • Have a nice time!

      • I don’t think James is human. I think he’s a supercomputer pretending to be human. He and Bob are engaged in some kind of high-level chess match that is beyond my feeble human capabilities. Luckily, their combined efforts to add to our articles make this site tremendously more valuable. 😀

        • There are a bunch of people, regulars, here that bring a depth of knowledge that benefits the community.

          Forgive my inability to remember how to spell unusual names – Larmion is an incredible information source, ‘ven’ has gotten on top of battery issues over and over, eeve brings the knowledge, Steve – EVs, ….

          That’s a short and very incomplete list. Apologies to all those who I missed.

          Over time we’ve built a group of people who want to learn. I see my job as to keep the site open to factual discussions and not let trash talkers take over.

          (James and I aren’t playing chess. I can’t play in his league.)

          • Haha, yeah, I didn’t want to start naming names, because there are so many and I know I’d forget some. But you and James are probably most prolific.

  • Some reasons to focus on cell efficiency:

    1. Reduction of racking and shipping costs
    2. Increase of roof power per sq ft.
    3. If 30% of roofs were formerly suitable, now 40% will have some space that is usable.
    4. The 40% of houses can produce enough for another 20% of houses (50% excess production even with storage self use of 100%)
    5. Possibility then of a total of 60% residential powered by roof top solar.

    6. Parking lot pv contributes more for EV charging because of higher energy density.

    • Reduction in labor, cover glass and framing material.

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