Indium Tin Oxide (ITO) has been the transparent conductor-of-choice for most display applications due to its superior combination of environmental stability, relatively low electrical resistivity and high transparency.  The fact that it gets high marks on these performance characteristics has also meant that it has also become the benchmark for other emerging applications -- such as photovoltaics -- that need transparent conductors.

The Indium Scare
However, ITO is far from the perfect solution to many transparent conductor needs and a surprising number of firms are looking for ITO substitutes.  The most frequently cited reason for this quest is that that the price of ITO is seriously impacted by the price of indium, which has risen significantly in the past few years, precisely because of the growing demand for ITO.  From prices measured in the tens of dollars per kilo, the price of indium has risen to almost $1,000 per kilo in the very recent past.  Consequently ITO is a much more expensive material than it used to be. 

However, while the impact of indium prices and availability have an undeniable effect on the market for and use of ITO, it is frankly hard to believe that all the current activity in seeking alternatives to ITO can be explained in this way.  For a start, for most display applications, ITO is just a few percent of the total bill of materials for display itself.  For a large flat panel display (FPD), having the extra cost of more expensive ITO absorbed somewhere along the supply chain is not hard to imagine.  The big display makers certainly don't seem too worried at the present time and few seem willing to make a strong commitment to ITO alternatives at the present time. 

There are horror stories about Indium prices leaping to $10,000 per kilo and this certainly might make a difference; although even then we might be talking about the percentage of the total bill of materials represented by ITO growing from three percent to 10 percent in very round terms.  And in any case there seem to be plenty of untapped indium reserves that would certainly come into play, not to mention increased recycling of ITO, if prices started to shoot through the roof as has been suggested by a few observers.  And, while the long-term trend for indium prices is surely up, at the time of writing indium prices have fallen significantly for the past few months, so the pricing situation with Indium is not a simple one.

Beyond Indium:  The New Transparent Conductors
Yet the fact remains that a surprising number of firms are selling - or at least researching - alternatives to ITO.  One explanation for this could be simply that such firms are simply looking for an new application for older materials and playing up the inadequacies of ITO in order to make a sale.  Or even worse, all the fuss about ITO substitutes might be just an example of a common trend with new technology; the solution chasing after a problem to solve.

NanoMarkets believes that this kind of cynicism certainly belongs in any complete explanation of what is going on the transparent conductor market today.  However, our research efforts have revealed that (1) ITO manufacturers are themselves dabbling with ITO replacements and (2) major display manufacturers have been open to carrying out significant trials of some of the more advanced ITO replacements.  This suggests to us that there are other more objective factors that are promoting the cause of alternative transparent conductors.

One of these factors clearly is that while the performance characteristics of ITO are adequate, they are really not that impressive.  Second, the sputtering process typically used to deposit ITO is wasteful and expensive.  While recycling can considerably improve ITO efficiency this in itself is an expensive process.  And, the way that ITO layers are currently created seems out of place in a world that is moving towards deposition and texturing using printing technology.  One way to move towards printing and stick with ITO is through ITO inks.  These have existed for some time, although their performance is not up to sputtered ITO.

This is not the only way in which ITO might be viewed as anachronistic.  Flexible displays are a tiny proportion of the display industry at present, but represent a major growth opportunity.  Unfortunately, it is not an opportunity to which ITO is well suited, because it cracks if bent too far.  Indeed, flexibility is likely to become a broader challenge for ITO, since flexible substrates are becoming a rapidly growing part of thin-film electronics and photovoltaics, not just in order to fabricate novel products such as rollable displays, but in order to perform R2R manufacturing.  With flexible substrates now being a major thrust of the printable electronics business, ITO seems increasingly less and less desirable.

Alternatives to ITO
There are a variety of technical approaches as well as strategic motivations for developing ITO substitutes.  Broadly speaking, however, there are three kinds of firms pursuing the ITO replacement opportunity:

• As we have already indicated, there are several firms that are heavily committed to ITO are researching alternatives to ITO behind the scenes either as part of an ongoing effort to improve the materials that they offer to their customers or as a defensive measure in case someone else comes up with a better method of doing transparent conductors.  Such efforts are not well publicized for understandable reasons.

• A second motivation is found among large materials firms that are already supplying materials that can be used as transparent conductors.  These are mostly firms supplying other kinds of metal oxides with similar properties to ITO, but with better price points or even ease of use.  However, there are also organic materials suppliers that have something to offer in this space.  All of these materials manufacturers are essentially pursuing the ITO replacement market as a new way of selling what they already have.  A good example here would be H.C. Starck's efforts to promote PEDOT as a transparent conductor.

• There are also a few firms and plenty of research groups that are looking at novel ways of replacing ITO as a core value proposition.  The firms that are usually talked about in this regard are Cambrios, Eikos and Unidym, all of which are using nanomaterials.  There is a considerable amount written about these firms, but their future prospects remain somewhat controversial.  By common (but not universal) consent none of the nanotechnological approaches to ITO replacement have yet achieved many substantial improvements on ITO and in most cases they seem to have inferior performance.  This coupled with the unfamiliarity of the nanomaterials approach will doom such companies according to a few insiders.  The companies and research groups involved - not surprisingly - have higher hopes.

The final piece of the puzzle is delivery; it is not just the material itself, but the way that it is deposited.  As we have mentioned, sputtering is not an attractive manufacturing approach.  Within the framework of each material platform, manufacturers must ask themselves the question of how to move beyond sputtering.  This is an old question and, in fact, ITO inks have been available for some time.  Some of the other approaches to transparent conductors - the ones that use nanotubes, for example - are also looking at a printing approach to fabrication.

ITO Replacements:  First Apps
Flat Panel Displays (FPD):  No one - almost no one, anyway - sees the manufacturers of large HDTV FPDs abandoning ITO and running to an ITO replacement anytime soon.  Such manufacturers are understandably conservative.  With huge, and hugely expensive, display factories in place they aren't about to change horses mid-stream.  In addition, since their entire business hangs on the performance of their products, there is not much incentive to abandon a relatively minor tried and tested material for something entirely new. 

Touch screens: Where almost everyone involved with ITO substitutes does see an opportunity is in the touch-screen display market.  Here the market and technical parameters a different from the FPD television market.  In particular, for this type of product, the market is looking for a high-degree of resilience.  We have all had the experience of working with aging touch screen displays that need to be poked rather than touched and this will often be because the ITO layer is wearing out.  Certain replacements to ITO offer better performance in this regard.  In addition, the proportion of the bill of materials represented by ITO in touch screens is higher than for larger FPDs, so the impact of indium price rises matter more.  Transparency and conductivity requirements are not as great for touch screens as they are for televisions, so the performance of some of today's more obvious replacements for ITO would work well enough in this application.  Finally, the touch screen business is growing quite fast, which, also makes it attractive to ITO replacement advocates.

Beyond displays:  Touch-screen and (to a lesser extent) flexible displays are certainly motivating much of the work on ITO at the present time, but there are other areas that are also seen as opportunities.  One of these OLED and EL lighting, which is, of course, closely related to the display application and has fairly similar performance criteria.  In particular, a considerable amount of money is being plowed into solid state lighting and because of this - and the difficulties associated with fabricating AMOLEDs - many OLED makers are turning to lighting applications instead.  It is understandable, therefore, that manufacturers of transparent conductors would follow a similar path.

The other area of some potential importance is photovoltaics.  Again this is a "hot" area from a marketing perspective, but is also one where the materials aspects of front conductors are an issue.  With newer thin-film photovoltaic (PV) materials, transparent conductors are required and, while ITO is being used, alternatives are certainly being considered.  One area of special opportunity here is Copper indium gallium selenide (CIGS) PV, which apparently needs a transparent conductor and has exceptional growth potential because it offers both the virtues associated with thin-film PV and conversion efficiencies that are not too far off those associated with conventional crystalline silicon PV.  In addition, the feeling in the industry is that since manufacturers of newer thin-film PV products are already working with new materials, they may be more amenable to working with ITO replacements.  They certainly don't have the commitment to ITO that a display maker would.

Finally, there may be some opportunity for new kinds of transparent conductors in a range of optical and electronic coatings.  This has always been one market in which ITO has been used to some extent.  We have not found much interest in this area from firms pitching ITO replacements, but it would not be a surprise to see such firms find early customers in this area.

To summarize then, ITO represents an industry standard transparent conductor that is rising in price and has adequate but not exceptional performance.  No other material has yet appeared that can seriously challenge ITO in a broad sense and it is not even clear that such a material will ever appear.  However, it seems that there will be important future opportunities - perhaps no more than niches at first, but growing into something bigger - for alternatives to ITO.   As we have noted, ITO does not seem well suited to the next generation of display, lighting or PV products and all of this has set off a search for replacements using conventional materials and nanomaterials.   Any there are plenty of candidates for ITO replacements ranging from a large family of other metal oxides, through PEDOT to sophisticated nanomaterials and nanocomposites.

This article is an excerpt from the Nanomarkets report The Future of ITO: Transparent Conductor and ITO Replacement Markets.  For more information about the report, visit NanoMarkets website at www.nanomarkets.net or email sales@nanomarkets.net.