Materials Markets for Thin-Film and Organic Photovoltaics

NanoMarkets will be releasing a new report that addresses the market opportunities for materials in thin film and organic photovoltaics. See Here for details.

In a recent NanoMarkets report we projected that the TFPV business would grow from approximately $1.6 billion in 2008 to over $7 billion in revenue in 2015. However, much of the important work in this space is happening at the materials level which will define who wins and who loses in this space. From improving energy conversion efficiencies to increasing device lifetimes to reducing costs, materials are going to be crucial. Not only will developments at the material level impact the core photoactive layer but they will lead to improvements in electrodes, substrates and encapsulation; materials will ultimately decide whether or not TFPV products will succeed in the market technologically and economically.

TFPV materials of all kinds are being led along interesting - and potentially profitable - new paths by the development of nanomaterials. One of the most important of these directions is PV inks. Printing PV with these inks is among several new manufacturing approaches being brought to bear on TFPV and that require new kinds of materials and we would expect to lead to new business revenues for materials firms.

The opportunities for materials suppliers in TFPV are usually defined in terms of four types of active materials used to create the photoelectric effect with amorphous silicon (a-Si) the most prominent. Indeed, until just a few years ago TFPV was largely identical with a-Si and the alternatives to a-Si were seldom seen outside of the lab and seemed as futuristic as some of the so-called Third Generation PV does now. Outside of a-Si there is CIS/CIGS, a class of materials that has really only just entered a true commercialization phase, but which promises to improve on the cost/performance achievements of a-Si. The fact that Nanosolar, one of the most prominent (and well financed) CIGS firms, is using printing as part of its process adds another dimension to the excitement around this material. Here is a real application of printed electronics with volume capacity in place.

The other two classes of materials that make up the world of commercialized TFPV are CdTe and organics (or hybrid organic/inorganic materials.) The CdTe story is similar in many ways to the CIGS story, it is about a relatively complex inorganic molecule that appears to have a way to take share from the a-Si TFPV establishment. Organic PV (OPV) is a different story altogether. Potentially, OPV can offer very low cost PV on flexible substrates, but with reduced longevity and reduced peak efficiency. (OPV's relative efficiencies in low light conditions can be quite good, however.)

The competitive battle between these approaches is usually cast in terms of competition between the solar panel makers' differing materials strategy, but has implications at every level of the value chain. Different materials supply structures have evolved to supply each of the four differing kinds of TFPV, although there are overlaps. If one considers the a-Si sector, for example, there is already a well established supply chain in this part of the TF PV business and at the materials levels the firms that stand to lose or gain are frequently large silane gas feedstock suppliers for photovoltaic applications. If one looks at the OPV segment there is a quite different group of firms making the required materials and a fuzzy line between the manufacturers of the materials and of the cell arrays themselves.

While any discussion of materials for TFPV will naturally be focused on the core photoactive materials, the market for TFPV materials is really much larger than that. Output from the TF PV sector is likely to reach a point in the next few years that this sector will be of interest to suppliers of other kinds of materials. For example, the manufacturers of various forms of transparent conducting oxides (TCOs) that are widely used in top contacts should be interested in what is going on in TFPV, which increasingly represents a volume opportunity for the materials they have to offer. TF PV is, for example, one of several areas where ITO replacements are a hot topic. Yet another important materials market derived from the TFPV industry is in the coatings, adhesives and other products designed to weatherproof solar panels. This area has assumed enormous importance in the OPV sector, because of the vulnerability of OPV to oxygen and water vapor. Cost effective encapsulation and barrier coating materials are materials that are in strong demand from this sector.

Then there are the substrates themselves. Traditional PV, including a-Si TFPV, makes regular use of glass substrates. However, in the past eighteen months a hot button for TFPV has become the availability of flexible substrates and the materials used for such substrates are most likely to be either some kind of plastic, such as PET, or foil. The reason for wanting flexible substrates in the first place is in part to facilitate R2R processing and in part to create entirely new products such as solar curtains and tent material.

The fact that the competitive battle between TFPV cell makers is being fought to a large extent at the materials level and that the growing market for TFPV is opening up new opportunities for materials other than the main photoactive material immediately raises the issue of the kinds of innovations that the market is looking for. Some of these are not materials innovations at all - novel device structures and optical enhancements - are examples. But many are.

Novel developments have even proved possible in the most mature of the TFPV segments; a-Si. Here, for instance, we have seen improvements in the blue response of a-Si using various kinds of doping, and the use of microcrystalline silicon in multi-junction devices to improve efficiencies. Innovalight's strategy of creating TFPV with silicon inks is just one of a number of improvements that materials firms are expecting by applying nanotechnology to PV materials. In the CIGS area, nanomaterials are being used to make printable precursors that are crystallized into CIGS. And nanotechnology may be road to PV moving into many different new markets. For example, researchers at the Center for Sustainable Energy Systems, Australian National University have been developing a "sliver solar cell;" actually a very thin single crystal silicon solar cell that promises to slash the cost of solar panels.

But while novel materials will surely play a role in the shaping the future of the TFPV materials sector, this sector will also have to keep its eyes on the ball as the TFPV industry experiments with new forms of manufacturing from specialized forms of vacuum deposition to flexo printing. These new production modes will require not so much different kinds of materials as new formulations. The art of PV ink making, for example, is only just being understood. And various commercial firms and university departments are seeking out improved ways of depositing organic materials for OPV and organic electronics more generally; the challenge here being to create processes that do not thermally destroy the materials while the deposit them.

And then there is the growing issue of environmental friendliness. If TFPV is part of our effort to "save the planet," it surely shouldn't use environmentally unfriendly materials in the process. This is worry with CdTe, since Cadmium is poisonous. But as the defenders of CdTe have pointed out a-Si and CIGS are not without their problems in this regard either. For now OPV occupies the high ground, in that the materials that it uses fall apart quite quickly in the air and the damp; exactly what TFPV manufacturers are trying to avoid in order to make their products useful!