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As simple as IBC – pv magazine International


From pv journal 03/23

IBC photo voltaic cells have been conceived within the Nineteen Seventies and the concept behind them is easy: Transfer all of the contacts, metallization, and different inner parts of the cell to the again aspect, leaving the entrance, energetic layer intact. closed and open to plenty of daylight.

That method ensures that the IBC, and different back-contact sort units, can push nearer to the sensible restrict for single-junction silicon cell conversion effectivity than different cell architectures. That objective has saved them centered on researchers, with lots of the highest in-lab efficiencies coming from back-contact buildings.

Processing back-contact cells at scale, nevertheless, has confirmed tough and costly. The ensuing lack of adoption signifies that comparisons of mainstream approaches are tough. “As the size of the again contact is small and is especially utilized in distributed technology tasks that preserve a greater look, it has a better premium,” stated Corrine Lin, principal analyst. of market intelligence firm rebranded InfoLink. “Based mostly on present producers’ product pricing, there may be sometimes a premium of $0.01/W, or increased, in comparison with PERC [passivated-emitter, rear contact solar]. Nevertheless, there isn’t any clear premium index as a result of small buying and selling volumes and totally different goal markets.

Most main producers have taken a less complicated route to enhance effectivity, however with less expensive strategies which can be approaching exhaustion – and researchers at Germany’s Institute for Photo voltaic Power Analysis Hamelin final 12 months calculated again -contact units can hit 29.1% effectivity – the renewed makes an attempt to commercialize again- Contact cells can be found.

IBC benefits

The US firm SunPower Company has been manufacturing IBC cells for over 20 years. Its merchandise are notably profitable within the residential market, the place aesthetic look and superior effectivity and reliability are extremely valued, leading to a premium value. In 2020, SunPower spun off its manufacturing enterprise to type a brand new firm, Maxeon Photo voltaic Applied sciences, which continues to fabricate IBC merchandise underneath the SunPower and Maxeon manufacturers.

Doug Rose, vp for know-how technique at Maxeon, explains that the again contact construction allows full optimization of the entrance floor, maximizing cell brightness and minimizing recombination, as a substitute of getting to additionally optimize for steel protection and lateral conduction in steel fingers. . On the again aspect, IBC permits for thicker steel, leading to decrease sequence resistance.

Rose added that, together with effectivity, superior reliability can be a spotlight for Maxeon, and having a premium product permits it to make design and supplies selections that lead to superior reliability. than standard – it presents a product assure of as much as 40 years in some. markets.

A key benefit of Maxeon’s IBC merchandise is that they’ve a singular, non-destructive reverse-bias habits. This prevents hot-spots – which might trigger harm to cells and modules – even in partial shade with failed module diodes. “We consider it gives added worth and differentiation and we’re placing loads of effort into extending the benefit of this space to our future generations.” Rose additional explains that the power to do that is one other inherent benefit of again contact know-how, though not all again contact architectures.

State of play

There are excessive hopes for back-contact photo voltaic. Radovan Kopecek, co-founder and director of the German institute of the Worldwide Photo voltaic Power Analysis Middle (ISC) Konstanz, stated pv journal in November, IBC modules could meet up with TOPCon (tunnel-oxide, passivated contact) merchandise in 2028 and make up half of the market in 2030. Some market observers are much less bullish however agree that the again contact applied sciences will probably see progress within the subsequent 5 years.

“Steady enhancements in manufacturing processes and effectivity have led to a gradual discount in prices for many back-contact applied sciences,” stated Karl Melkonyan, senior analysis analyst at enterprise intelligence agency S&P International Commodity Insights. “A big value discount, nevertheless, will take loads of time to totally develop. It may very well be a big discount in silver consumption; or a complete alternative of copper or aluminum; or further advances in soldering and cell interconnection processes, and different enhancements in effectivity, yield, and availability.

S&P International predicts that back-contact photo voltaic may obtain a 15% market share within the subsequent 5 years. InfoLink expects progress of round 5% within the subsequent two to a few years however little after that. “For the long run, its market share is unlikely to succeed in the size of PERC or TOPCon as a result of complicated course of and better manufacturing prices,” Lin instructed InfoLink. “Even when there may be nonetheless demand for back-contact – as a result of excessive effectivity and higher look – its market share is unlikely to succeed in 10%.”

Maxeon pursues such enhancements within the manufacturing course of. “Maxeon has a very proprietary course of with a number of patents defending the strategy,” stated David Smith, a scientist at Maxeon’s California R&D hub. “The processes we’ve got in pilot manufacturing now use extra mainstream gear, so we will journey the coat tails of the TOPCon business. We use these large, high-powered units as a lot as doable and our new technology makes use of a better proportion of these than earlier than.

Save and scale

Maxeon, nevertheless, continues to be centered on prospects who can pay a premium for efficiency and aesthetics, and says it would proceed to concentrate on its product vary, whilst extra of the IBC applied sciences debut. to look.

ISC Konstanz believes that the associated fee reductions required to help IBC’s robust expectations will be realized. The analysis middle developed “Zebra” IBC cells which can be in the marketplace by way of manufacturing companions in Europe and Asia, and proceed to decrease manufacturing prices and enhance effectivity.

“Our goal is that, from the associated fee construction perspective, as a lot as doable with normal know-how,” stated Joris Libal, ISC’s challenge supervisor for know-how switch. “We wish to begin with low cost processes, straight from the toolbox, and attain excessive effectivity.”

Valentin Mihailetchi, chief of the n-type group [negatively-doped] cell R&D at ISC Konstanz, went on to clarify that Zebra cells are made utilizing typical processes together with tube diffusion, display printed metallization, plasma enchaced chemical vapor deposition, and laser ablation, including, “It is about to make use of the processes which can be already established, in a barely totally different method.” That method can deliver extra advantages as a result of the back-contact structure will be mixed with passivating contacts and different cell designs, providing one other path to mass manufacturing.

Consumption of silver

In addition to processing prices, IBC cells require silver contacts for a similar polarities. “In comparison with p-type [positively-doped] PERC, there could also be 5% extra value for the wafer and a slight distinction within the depreciation of the gear as a result of there may be much less gear in comparison with PERC or TOPCon,” stated Libal. “The principle distinction is the price of the steel.”

With little have to make its back-side fingers as skinny as doable within the back-contact cells, nevertheless, ISC Konstanz makes use of copper paste as a substitute of silver within the screen-printing course of. Typical producers, in distinction, have to make additional enhancements in copper plating processes to scale back the silver content material.

Whereas ISC Konstanz’s IBC cells nonetheless require silver for contacts – copper can’t be in direct contact with silicon – Libal says that silver consumption will be decreased to lower than 5 mg/W to provide capability. cell. That is a fraction of the quantity utilized in PERC and TOPCon cells and helps ease business considerations about silver provide.

The analysis institute is engaged on the copper display printing course of and says it has achieved good ends in accelerated testing up to now. “The Zebra IBC cell with copper metallization can be a breakthrough that can lastly deliver the price of the IBC under PERC, with the effectivity nonetheless above,” stated Libal. “If these fundamental value and efficiency parameters are met, that is when it would fly.”

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