Discussions about profitability in the solar industry always ponder on lowering cost and driving up the efficiency of solar components. Conversely, both ideas have been contradicting each other, as efficiency always leads to higher processing and material costs. Although monocrystalline modules continue to lead on efficiency scales, for the above reasons, the price-to-efficiency ratio has not favored them as an item of choice during times of ASP collapse. For the last two years, Yingli Green Energy Hold. Co. Ltd. (ADR) (NYSE: YGE) has invested in n-type monocrystalline cell development, used successfully in PANDA-branded modules. While the company developed industrial production lines worth 600MW in capacity using n-type mono technology, last year’s capacity growth was made in multicrystalline products, reflecting tougher times, Chinese demand and hope to drive the cost further down. ECN, the company essential in Yingli’s move to n-type products just last month, visited China to promote its technology capable of obtaining 20% efficiency, with the roadmap leading to 22%.
Dr. Ye Zhang-Steenwinkel, Consultant Technology Transfer and Business Developer for ECN-Solar Energy, a department of Energy research Centre of the Netherlands (ECN), agreed to discuss n-type technology with SPVI.
SPVI: Dr. Zhang-Steenwinkel, our understanding of n-type technology is that the boron dopant used in production of the wafer in p-type is replaced by phosphorus. In comparison to legacy p-type processes, we read about challenges with creating the emitter using boron and difficulties using silicon nitride when creating passivation. Yet, new techniques like ion implantation and atmospheric pressures chemical vapor deposition (APCVD) have removed those obstacles. Can you please walk us through those concepts?
ECN: Indeed, it is well known that for n-type solar cell technology, to create cost-effective, homogeneous boron emitter is challenging, since boron behaves differently than the common phosphorus process. Tempress, ECN and Yingli have solved this issue and the same quality boron emitters can be made in full production at similar costs as phosphorus emitters. In combination with silicon nitride, to create passivation layer is even more difficult. ECN has invented a new passivation process and that is now implemented in PANDA. Alternative emitter processes like ion implantation and APCVD deposit boron in a different way. For those technologies, a homogenous boron layer can be deposited. But it doesn’t form a working emitter yet. Therefore, an extra annealing process is required. That requires an intensive research program in order to find the right combination of input power, doses and annealing conditions. So far, it still stays in the R&D phase. ECN cooperated together with Tempress, and developed a smart and simple process, the so-called B/P co-diffusion process. This process uses well-known industrial diffusion equipment. This process, in combination with our excellent passivation process before silicon nitride deposition, boosts n-type performance in excess of 20%. ECN has obtained the patents for both processes. ECN is certain that this is a very effective and cost-efficient industrial process. Alternatives still have to show the same level of cost effectiveness.
SPVI: What are the benefits of the n-type cells in comparison to p-type mono cells? Can you describe the opportunity for a bi-facial module option?
ECN: The benefits of the n-type cells in comparison to p-type mono cells are: (1) much higher material quality; therefore, n-type material has exceptional potential for high-efficiency commercial solar cells; (2) no Light Induced Degradation (LID) occurs in n-type; for p-type, up to 1% absolute efficiency degradation has been observed; (3) suitable for IBC cell concept due to the very high lifetimes. IBC on p-type is not possible; (4) better low light response in comparison to p-type. Further, it is suitable for bifacial cells and bifacial modules. For Solar Farms, bifacial can be very important. By choosing the right background, the power output can be increased by 20%.
SPVI: You have advertised that standard cell and module equipment can be used to produce n-type product; can you explain if any modifications are required, particularly since improvements of efficiency call for stencil printing instead of screen print metalization? Can you tell us whether there is good access to n-type wafers globally and explain the cost-benefit ratio for n-type wafer over p-type?
ECN: A standard cell line can be upgraded to an n-type production line by modifying the diffusion process and the addition of a rear side silicon nitride layer. Full aluminium deposition can be eliminated. I would like to mention that by eliminating Al on the back side field, thin wafer can be used that can reduce the production cost. For the module part, indeed, the conventional module equipment can be used for n-type module production. The advantages of the use of stencil printing are reducing the Ag consumptions, resulting in production cost and reducing the shadowing, leading to increased fill factor. Stencil printing is not new and can be easily implemented on standard screen printers. Using stencil, we have been able to boost efficiency by almost 1% absolute and reduce the amount of silver by more than 50%. Silver consumption for n-type is now the same as for p-type. Regarding the n-type wafers suppliers, it is accessible globally. Many experienced wafer manufactures are able to produce n-type material. The cost of making n-type material is, in principle, not more expensive than making p-type mono. However, due to the higher power output from n-type cell in comparison to p-type, the cost per watt peak is actually lower than p-type.
SPVI: To date, ECN and Tempress have been cooperating with Yingli. Does your current activity mean the technology is no longer exclusive to Yingli? Of late, Yingli had shown MWT (metal wrapped through) technology in their presentations, and Canadian Solar Inc. (NASDAQ: CSIQ) has advertised MWT modules. Is ECN involved in those developments? What is the cost to implement this type of cell structure and further benefit of doing so?
ECN: We still work very closely with Yingli, aiming for boosting the cell/module performance to higher levels along with significantly reducing the production cost. We have had a long and pleasant working relationship with Yingli and all our improvements are tested in pilot production at Yingli. This is a great benefit for us, since we can offer mature and tested technologies to our customers. We all have the goal to push the PV industry to the next level in terms of being mature, healthy and competitive and much higher efficiencies and lower costs are needed. Nobody can achieve this by themselves and it is a good development that more and more partners are involved and supporting the development of n-type. Regarding MWT, ECN develops MWT technology and process flows and ECN is the owner of the IP. CSI bought a license of our MWT technology. ECN is pushing the MWT development both for p-type and n-type. The benefit of applying this cell and module technology is significant. On the module level, by using ECN’s conductive back sheet concept, power output can be boosted up to 10%. For instance, the cell to module losses (CTM) can be reduced from 3-5% down to less than 1% for MWT. ECN’s equipment partner is Eurotron of the Netherlands. They sell both semi- and fully automated MWT module assembly equipment. The benefit of implementing MWT now is that it can be applied for thin wafers and full back contact cells like IBC (Interdigitated back contact cells, like SunPower). Since everybody has IBC on their roadmap, it makes sense now to start producing with MWT technology.
SPVI: In your recent pamphlet you talked about “proven” low cost of production. Could you describe overall cost ratio in comparison to p-type mono and p-multi technologies?
ECN: Here, I would like do the comparison between p-type mono and n-type mono, since the wafer production method is the same and n-type wafer production costs should be very close to p-mono. For this reason, comparison between p-mono and n-mono is more logical. As we all know, the current market situation is depressed. In our opinion, the recipes for survival for PV manufacturers are reducing cost and increasing module efficiency. High efficiency at low cost is a must. The benefit of 1% absolute higher efficiency is 10% higher price in $/Wp. Many leading PV companies are working hard on that. The most current cell technology improvement is based on p-type mono and average efficiency is about 19%. For n-pasha, our offering leads to 20% average efficiency. Cell processing costs for p-type and n-type are almost the same since this is dominated by the silver consumption. Our development efforts have reduced silver consumption to the average usage for p-type. However, p-type material has an LID problem. The higher efficiency on p-type, the higher the LID effect is. In contrast, n-type material doesn’t have such a problem; since the dopant is phosphorus instead of boron, no boron-oxygen complex is formed. Therefore, the overall cost per watt peak for our n-pasha is actually lower than p-type and the selling price is higher than p-type because of 1% higher efficiency. In this way, our customers can have much larger margins producing n-pasha.
SPVI: In your recent announcement you described a workshop you held in Shanghai, which was attended by JA Solar Holdings Co., Ltd. (ADR)(NASDAQ: JASO), Suntech Power Holdings Co., Ltd. (ADR) (NYSE:STP) and LDK Solar Co., Ltd (ADR) (NYSE:LDK) representatives. Could you tell us about the expectations of the Chinese customers and what particular benefits for Mainland manufacturers would n-type technology offer? In pursuit of differentiation, how exclusive can your offer become?
ECN: Indeed, there were many leading PV companies attending the workshop during 8th CSPV conference in Shanghai. I think all Chinese customers are looking for the next advanced, but cost-effective technology. It is well known that the Chinese PV industry has a shortage of technology differentiation. For that, ECN can play an important role, on cell, module and system. The expectation for most leading PV companies is the PV market will pick up slightly later in 2013. So, now is the time to invest in the next generation cell/module technologies, like n-type and MWT. The strategy will be to have these technologies in house; once the markets pick up, it can be implemented immediately. Under this condition, ECN can offer the Chinese companies our n-type cell technologies based on low cost and high efficiency. ECN will form joint forces with them together with our industrial partners (equipment suppliers, material suppliers, etc.) to work side by side to tailor the technology toward a differentiated product offering. It can be a technology transfer for our n-pasha. It can be a joint development project for n-MWT and IBC type. Also, it can be a new concept implementation on module like MWT. I think the advantage of our offer is that our offer is NOT exclusive. Our technology is accessible and acceptable by everybody and a whole value chain is developing this technology further. Companies should not differentiate on the technology in the module; they should differentiate in the product they offer to the market! To be the only one worldwide who can produce this type of cell doesn’t secure the legacy at all. It just means you have to secure all investments in R&D by yourself to make sure that the technology stays cost competitive!
SPVI: Globalization of the solar industry is living under the shadow of tariffs and trade disputes. China is definitely the largest manufacturer of cells and modules globally, but very soon all of those may have a tariff in the EU. How do European and American companies see the potential threat of limiting intellectual property when trading with China?
ECN: There are always threats and chances, but standing still is no option. China is by far the biggest producer of PV, and in 2013, China will be the biggest market for PV. These immense developments in China result in large technological and economic progress in PV in the West. It is very important to take part in these developments (and not ignore them), work together and in this way ensure a prosperous future for PV globally. Countries and markets investing in new PV technologies are the engines for progress. ECN is working together with (new) markets, like China or the United Arab Emirates. ECN sees itself as pivotal in binding the West and China together. We work very closely together with all major suppliers to the PV industry, like Tempress, Rena, and Heraeus. On the other hand, we also work very closely together with the leading PV producers in China. In this way, everybody benefits: the West gets high technology development and economic progress, China gets to produce the best PV panels, and the World gets the cheapest possible solar electricity. Two things that ECN does are: (1) secure and protect the IP; (2) move ahead to develop more advanced technology and know-how. One of the positive aspects coming out of this situation is that the West is forced to be creative and innovative in order to keep advanced position in technology and to hold its know-how secure.
SPVI: Thank you for much for your time. Looking forward to your future collaborations in China and globally.
ECN: Thanks for this opportunity to share our view on PV and the later development and our technology with the readers. I’m looking forward to having such conversation in the near future.
This interview was conducted by Robert Dydo, and edited by Senior Editor of SolarPVInvestor, Stephanie Pierce.
