How Long Can TCOs Reign in the PV World and What Comes Next?04 Nov 2011 • by Natalie Aster
The market for transparent conductors sold into the photovoltaics (PV) sector for electrodes is currently made up of transparent conducting oxides (TCOs), including indium tin oxide (ITO). PV, however, is the first major high-performance application for transparent conductors to largely shake its dependence on ITO in favor of less-costly TCOs, mainly tin oxide- and zinc oxide-based materials. This places the PV industry in the somewhat comfortable position of having relatively few cost incentives for making changes to the transparent conductors used; the status quo—TCOs—are already cheap.
However, this should not be taken to mean that there is no incentive for PV manufacturers to switch to other transparent conductive materials, or even that there is never a cost incentive to do so. Indeed, while non-ITO TCOs are cheap from a materials point of view, the processes used to form coatings with them are certainly not cheap. Sputtering equipment and other similar vacuum deposition equipment is expensive, and the energy required to achieve the deposition conditions is certainly costly as well.
Thus, the next major shift in transparent conductor usage will be toward materials that can be deposited by cheaper methods—printing and coating, although obviously PV manufacturers will not pay heavy premiums for materials that can be processed in this way.
Opportunities for ITO Firms—Are There Any?
ITO has been displaced by tin oxide and zinc oxide to a large degree in the PV industry, but there are still significant amounts of ITO used. NanoMarkets believes ITO will continue to see a declining penetration over the next eight years. But because the PV sector itself is growing, the revenues that ITO suppliers will derive from the PV sector will continue to grow as will the volumes of the material shipped into the sector.
The reasons for this thinking are: (1) ITO can still claim to offer superior transparency compared to other TCOs, and (2) because of the development of market segments that favor “premium” products. One good example of where ITO is likely to be used is in BIPV glass. BIPV is close to being a luxury product and is one where transparency is important for obvious reasons. In addition, in BIPV glass, the cost is dominated by the glass itself so the cost of ITO is not such a big deal.
NanoMarkets believes that the PV technologies that will use the most ITO will be OPV and DSC. This is despite the wide perception that these technologies will be made or broken primarily by the cost points that they can achieve. In fact, OPV and DSC look less and less like they will be able to offer major cost improvements and their commercial success is now completely dependent on their ability to exploit their unique characteristics—primarily transparency and flexibility. Transparency gives OPV/DSC an opportunity in the BIPV glass space and we have already noted why ITO might claim that market. But we also noted that OPV/DSC no longer has cost as part of its stated unique selling proposition, so at least ITO is not going to be ruled out immediately on cost grounds.
Transparent Conductor Markets 2011
Published: July 2011
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Opportunities for Other TCO Firms in the PV Space
NanoMarkets believes that non-ITO TCO firms catering to the PV sector will see their volume shipments and revenues grow over the next eight years. This is because substitution of ITO with other, less expensive, TCOs remains—and it will continue to throughout the forecast period—a major trend for transparent conductors in the PV industry.
And while other transparent conductors—printable ones, conductive polymers and nanomaterials—will make some inroads into the PV market, the extent of their penetrations will not be enough to significantly concern the TCO industry. The market share that is captured by these printable materials will remain quite small throughout the period considered in this report. This is especially the case for the largest volume PV technologies in the thin-film PV space: CdTe and TF-Si. The volumes they achieve will be significant for the firms involved, but not as significant for the TCO firms from which they capture share.
Non-ITO TCO firms have the opportunity to increase volumes by supplying the growing PV technologies that already use them—CdTe, thin-film silicon, and CIGS. But they also have the opportunity to gain new footholds with two PV technologies that currently use only ITO: namely OPV and DSC. Not all OPV and DSC applications are as well insulated from PV cost as BIPV is; in fact, many will remain very sensitive to cost. TCO suppliers can gain volumes and make money by helping OPV and DSC move away from ITO in these applications as part of their cost reduction efforts.
Opportunities for Nanomaterials and Conductive Polymer Firms in the PV Space
Nanosilver-based transparent conductive films are on the verge of an opportunity not seen in the history of the transparent conductor industry: the ability to produce films that are both more transparent and more conductive than ITO, in commercial quantities and at lower cost. The importance of this development in the long run cannot be overestimated; it will eventually have major implications for all of the industries that use transparent conductors.
Carbon nanotube-based transparent conductors appear to be approaching a similar game-changing opportunity in the long run. Although the carbon nanotube itself is quite new and still not yet fully understood, it seems likely that these carbon nanotube-based materials will produce commercial-volume films exceeding ITO’s performance just a couple of years after the nanosilver ones do.
In the short run, adoption of such new technologies will almost certainly be rather slow and deliberate. In the PV industry, the differences in deposition processes between these nanomaterial-based materials and the standard TCOs are substantial, and somewhat risky considering the low cost of the non-ITO TCOs they would displace. NanoMarkets sees an opportunity for these materials to capture a two-percent share of the transparent conductor market in PV by 2014. And because the cost of these films is mainly in the value of the materials rather than the cost of depositing them—as is the case for TCOs—that two percent share will produce 10 percent of the transparent conductor revenues in the industry.
Conductive polymer firms also have opportunities for growth in the PV market, even though their low cost means that the revenue-generating potential is relatively small. The best opportunities are in OPV and DSC, in part because OPV already widely uses the same conductive polymers as hole injection layers/planarization layers between the active material and an ITO electrode. But both OPV and DSC will also benefit from these conductive polymers because both flexibility and cost are critical to many of the applications in which they are to be used, more so than PV performance. As OPV shifts away from ITO and the need for HILs shrinks, the new electrode application of these materials can help to fill in the gap and even grow volumes and revenues beyond what was generated by the HILs.
How New Developments in the Transparent Conductor Space will Create Opportunities for PV Panel Makers
Among PV panel makers, the development of the transparent conductor industry will produce opportunities to reduce costs and improve performance. The most immediate opportunity for PV panel makers is for thin-film silicon, OPV, and DSC manufacturers, the ones that still use ITO mainly because of its legacy. These firms have the opportunity to reduce costs by switching from ITO to one of the lower-cost TCO— tin oxide or zinc oxide. Doing so could save over 75 percent of the materials cost of the ITO, an amount that fluctuates with the price of indium and ITO.
A major approaching opportunity for PV firms is to use printing or coating to deposit the transparent conductors instead of sputtering or other vacuum deposition techniques. The advantage of doing so is not in the savings on materials cost—when the alternative is a low-cost TCO like zinc oxide or tin oxide—but in reducing the cost of applying the materials. This opportunity covers three classes of transparent conductors: conductive polymers, nanosilver-based films, and carbon nanotube films. There have also been attempts to print both ITO and other TCOs, but the commercial impact of such work seems to be negligible.
Conductive polymers: PV manufacturers have the opportunity to use conductive polymers in this regard, offering the greatest potential savings among the transparent conductive options. Manufacturers that take advantage of this route will maintain materials costs similar to those of the inexpensive TCOs, but will take full benefit from the lower cost of printing versus vacuum deposition. But this opportunity is mainly one for devices that do not require high performance, yet do require high flexibility and low cost. The conductive polymers are not very conductive or transparent in comparison to the other options, and devices using them would trade a performance hit for the lower cost and greater flexibility.
OPV is an especially good fit for using conductive polymers as electrodes because it already uses the same materials as HILs. In an overly simplistic approximation, using conductive polymers as electrodes would involve little more than leaving off the ITO layer.
Nanomaterials: The opportunities for PV manufacturers to use nanosilver- and carbon nanotube-based materials to print electrodes are geared more toward high-end flexible applications. These materials are the ones with the potential to exceed the transparency and conductivity performance of ITO and other TCOs. If they are able to achieve this higher performance, then there will be no performance hit for using them. And while these materials are not yet commercialized in any sense that is useful to determine initial pricing, NanoMarkets expects their materials costs to be higher than those of ITO, but for the low deposition cost to approximately make up for it.
Hence, the total cost of using nanosilver- and nanocarbon-based materials is likely to be greater than that of using tin oxide or zinc oxide. But this is still a major opportunity because it can enable high flexibility in products that rely on both flexibility and performance. This opportunity is closer—beginning in 2012 or 2013—for nanosilver films than it is for carbon nanotube films, which will begin to be used in significant volumes a year or two afterwards.
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