The Fraunhofer Institute for Solar Energy Systems ISE, Soitec, CEA-Leti and the Helmholtz Center Berlin jointly announced this week having achieved a new world record for the conversion of sunlight into electricity using a new solar cell structure with four solar subcells. Surpassing competition after only over three years of research, and entering the roadmap at world class level, a new record efficiency of 44.7% was measured at a concentration of 297 suns. This indicates that 44.7% of the solar spectrum’s energy, from ultraviolet through to the infrared, is converted into electrical energy. This is a major step towards reducing further the costs of solar electricity and continues to pave the way to the 50% efficiency roadmap.
Back in May 2013, the German-French team of Fraunhofer ISE, Soitec, CEA-Leti and the Helmholtz Center Berlin had already announced a solar cell with 43.6% efficiency. Building on this result, further intensive research work and optimization steps led to the present efficiency of 44.7%.
These solar cells are used in concentrator photovoltaics (CPV), a technology which achieves more than twice the efficiency of conventional PV power plants in sun-rich locations. The terrestrial use of so-called III-V multi-junction solar cells, which originally came from space technology, has prevailed to realize highest efficiencies for the conversion of sunlight to electricity. In this multi-junction solar cell, several cells made out of different III-V semiconductor materials are stacked on top of each other. The single subcells absorb different wavelength ranges of the solar spectrum.
“We are incredibly proud of our team which has been working now for three years on this four-junction solar cell,” says Frank Dimroth, Department Head and Project Leader in charge of this development work at Fraunhofer ISE. “This four-junction solar cell contains our collected expertise in this area over many years. Besides improved materials and optimization of the structure, a new procedure called wafer bonding plays a central role. With this technology, we are able to connect two semiconductor crystals, which otherwise cannot be grown on top of each other with high crystal quality. In this way we can produce the optimal semiconductor combination to create the highest efficiency solar cells.”
“This world record increasing our efficiency level by more than 1 point in less than 4 months demonstrates the extreme potential of our four-junction solar cell design which relies on Soitec bonding techniques and expertise,” says André-Jacques Auberton-Hervé, Soitec’s Chairman and CEO. “It confirms the acceleration of the roadmap towards higher efficiencies which represents a key contributor to competitiveness of our own CPV systems. We are very proud of this achievement, a demonstration of a very successful collaboration.”
“This new record value reinforces the credibility of the direct semiconductor bonding approaches that is developed in the frame of our collaboration with Soitec and Fraunhofer ISE. We are very proud of this new result, confirming the broad path that exists in solar technologies for advanced III-V semiconductor processing,” said Leti CEO Laurent Malier.
Concentrator modules are produced by Soitec (started in 2005 under the name Concentrix Solar, a spin-off of Fraunhofer ISE). This particularly efficient technology is employed in solar power plants located in sun-rich regions with a high percentage of direct radiation. Presently Soitec has CPV installations in 18 different countries including Italy, France, South Africa and California.
Very nice result. But the progress is not that amazing. As the article points out, this stacked cell approach is based on space solar cells. Boeing had a 37% cell with only 2 stacked cells back in 1989 ! So an 8% gain in 24 years with double the complexity.
Need to know more about this New Soar Cell and it’s commercial applications, prices etc.
What is concentration of “297 suns” in watts/sq.cm.?
1 sun is 1kW/m2 or 100mW/cm2, so 297 suns is about 30W/cm2.
That is impressive.
Soitec did not start “in 2005” or as otherwise cited here – just this recent CPV acquisition.
Now, critically, it seems the market needs to see if Soitec’s smart-cut process can make a $5 chip, and if it can make a much more robust chip than is demonstrated at the present 297 suns, say at 500+ suns, and at higher temperature cycling, at 0 – 100 Celsius.
It is a very significant jump in efficiency of III-V multiple-junction solar cells.
Cost reduction of solar power is a challenge for its widespread use. Will these III-V multiple-junction solar cells produce power at rate cheaper than now dominating monocrystalline silicon PV technology?
Thanks.
A. Kumar
I am so happy to hear this very good news. but there is some question on expenses of using such technique to create multifunction, using of III-V material, lifetime of such cell in a concentration construction and finally cost of electricity produced by using this technique.
This is an appreciable achievement. We wait from you more technological innovations towards higher efficiency solar cells. But what about the supply of the three five compounds? My congratulation for achieving the new world record of the solar cell efficiency.
The efficiency record is always fascinating. Yet what matters in practice is cost, which is hard to standardize and form a world record competition. For silicon module it is about 0.7$/Wp — How much does CPV have to pursue?
Back in the 1960’s when Westinghouse made some silicon web solar cells for satellites, we tried to make dual-bandgap solar cells out of GaAs on Ge and Si for example. But the satellites were the only market for solar cells for a while, and then as calculator energy sources. And silicon costs were still high since military markets dominated and kept Westinghouse from ever getting really efficient in making IC’s or Solar Cells. ( They even thought IC’s were too expensive to ever be used in computers, so no-bid a huge IBM request for quote.) The silicon web cells were pulled from molten silicon hanging between two dendrites, about 3/8 inch wide and many feet long (could even be spooled up). The single crystal nature was what made them exciting vs polysilicon sheets. They evolved during the 70’s and 80’s to some extent, but never made mainstream.
http://www.sciencedirect.com/science/article/pii/002202487790152X is Westinghouse web for solar cell paper, still costly for some reason. This one is free: http://arc.aiaa.org/doi/abs/10.2514/3.23104?journalCode=jpp
Progress in solar cell efficiency has been incremental over the years as new materials and fabrication techniques have evolved. 44.7% efficiency is impressive given past solar cell performance over the years. Comparably speaking, Extreme UltraViolet lithography (EUV) has also evolved slowly as new materials and process considerations are evaluated. I suspect we’ll see continued incremental progress in solar cell efficiency, with time lines for further improvement contingent upon our successful challenge of conventional physics.
World record PV conversion efficiency is always an interesting topic, but articles like this can be quite misleading. For example, there is absolutely nothing in this article that supports the statement, “This is a major step towards reducing further the costs of solar electricity…” A four-color III-V solar cell that has twice the efficiency of standard single-crystal Si cell–but with (probably) orders of magnitude higher cost, is not, in any way, a step towards reducing the cost of PV generated electricity.
It is, however of interest in applications with weight and size limitations, such as solar-powered aircraft, particularly where the buyers are willing to pay a significant price for performance. Concentrator optics could be an obstacle to such applications; perhaps they can be made more compact using meta-materials.
Quick math… say 4 × 4 inch pv cell… or .12 sq. Ft. So 300 × .12 is say 36 sq. Ft. Mirror
That’s at least 2 kw worth of sun and so about 1000 WATTS of electricity. A very usable amount.
This is a very good idea. And for all those who say how expensive it is,,, LCD tv’s were too much?
Possibly a device for every home? Very similar to satellite dish but kicks out a kilowatt of power.
I say go for it! Full steam ahead!b
This is basically the Soitec process, developed back in the 90’s for SOI. It doesn’t surprise anyone involved in multijunction PV that a four-junction will perform, in “hero” cells, better than the well-developed three-junction. And if you make a five-junction, that will perform better yet, in a lab. The Soitec process can produce many different multijunction combinations, ad nauseum – the only problem is the cost.
The “297 suns” indicates pretty clearly that these assembled (not grown) 4-junction arrays are currently having reliability problems (it needs to handle much more concentration). What would be magnificent (rather than only academic), is if they can be made with a reliabillity and cost approaching the commercial 3-junction (with roughly 40% efficiency hero cells) that are grown from a single substrate (started by Boeing/Spectrolab and now “globalized”). It just doesn’t look very close to this goal at the moment.
Concentrator PV utilizes the direct normal solar insolation (about 850W/m2) not global insolation (direct plus dffuse = ~1k/m2). The early focus of multijunction PV and the corollary development of III-V material and device technologies was for terrestrial applications with the release of the Multijunction Concentrator PV Request for Proposal from Sandia Labs around 1977. One complexity of 4 junction PV is the changes in the solar spectrum over the course of the day (remember red sunrises and sunsets – loss of blue spectrum). If monolithic where the junctions are in series, the overall efficiency is constrainted by the current limited junction. I know because I started and managed these programs and had the privilege of working with remarkable people. PS. For highest conversion to useful energy, consider hybrid PV-thermal systems (see paper circa 1977-1978). I have nurtured many PV technologies over my career. I appreciate today’s achievements and commercialization of PV and renewables.
III-V technology: the up and coming technology just like we said in semiconductor land 30yrs ago. It is still up and coming. Not cost effective, too complex to manufacture for HVM and be used only for space.
Is this solar cell in real production now or just in R&D stage?