The Future of Thin Film and Organic Photovoltaics Manufacturing

The following article was drawn from NanoMarkets' upcoming report on The Future of Thin Film and Organic Photovoltaics Manufacturing

Thin-film photovoltaics (TFPV) and organic photovoltaics (OPV) have been with us for years, but until recently these technologies have been only niche activities.  TFPV has been most visible in the form of strips of amorphous silicon (a-Si), which are used to power calculators.  There has been little commercial activity for OPV so far. However this could be changing:  The marketing of small, solar power chargers using OPV had just started at the time of this writing.  Nonetheless, OPV has been an area of academic research for decades; it was one of the very first areas of organic electronics to be researched.

In the past three to five years, however, interest in both (inorganic) TFPV and OPV have grown considerably. The drivers have been all the factors that have promoted PV as a whole: renewability, low carbon emissions, price stability, tax incentives, feed-in tariffs and so on.  To this list, TFPV and OPV add (at least potentially) the advantages of low-cost, easier manufacturing and the ability to do that manufacturing on flexible substrates, which is a plus compared to the dominant crystalline silicon PV.   

The rise of TFPV and OPV has automatically put the spotlight on manufacturing issues.  Not that manufacturing was ever a minor point; a discussion of manufacturing is always to be found in technical papers.  However, the move of these technology/materials platforms from the lab to mass productionobviously raises new manufacturing issues.  In the new environment manufacturing emerges as a key strategic area for TFPV and OPV solar panels and opens up new opportunities for manufacturers of fabrication equipment.  And while NanoMarkets has discussed manufacturing issues to some extent in its other reports, we believe that at this time there is a need for a report geared solely to analyzing the manufacturing environment for TFPV and OPV.  This is the primary motivation behind the creation of the present report. 

There are four perspectives on manufacturing, in particular that we believe are critical to the TFPV and OPV paradigms, each of which point to different opportunities, and to which much of the analysis in this report is therefore devoted.

Perspective # 1: Manufacturing and PV Conversion Efficiencies

Each of the TF and organic PV approaches differ in many important ways, although, as already noted, they also share some common advantages. Unfortunately, they share a common disadvantage too: the conversion efficiencies associated with each are quite poor when compared with standard crystalline silicon (c-Si) PV. Actual numbers vary, depending on specific materials platforms and whether one is talking about cells developed in the lab or ones commercially available. There can be plenty of debate about what the "real" numbers actually are. But for inorganic TFPV, achievable numbers for commercial cells are around 12 percent, while crystalline silicon could offer almost 20 percent. Commercial OPV is probably closer to 5 percent conversion efficiency.

Understandably then the key goal at every level of TFPV and OPV commercialization is to improve on conversion efficiencies. We have already noted that different materials are associated with different efficiencies. (For example, CIGS, the most hyped TFPV approach at the moment, potentially offers all the advantages of thin film, along with conversion efficiencies that approach those of c-Si.) And it is not just the choice of photoactive material that can affect conversion efficiencies; many "champion cells" that offer superb performance in the lab, do so because they use exotic (which tends to mean expensive) materials for contacts. Cell designs are also a major factor in boosting conversion efficiencies. Indeed this is the primary point in coming up with a new cell design and it is the specialized cell designs associated with OPV that make OPV possible in the first place.

Manufacturing is central to all of the above. Manufacturing requirements are directly impacted by the choice of materials and cell structure. Conversely manufacturing choices directly enable or prohibit certain types of materials and cell design. Particular cell designs and materials strategies are optimized for particular manufacturing techniques. Traditional high-temperature deposition approaches—as opposed to the much-touted printing techniques—are often associated with better cell efficiency, but at higher costs, for example.

Perspective #2 Manufacturing and Cost Reduction

Cost/manufacturing platform trade-offs: This trade-off is critical in the OPV sector where, for example, G24i uses a very, low cost manufacturing technology (screen printing) to produce dye cell-based panels with low efficiency, which is good enough for applications such as mobile chargers. Contrast this with the manufacture of c-Si PV, where relatively high-cost (often also high temperature) approaches originally taken from the semiconductor industry are used to produce the best performance that any species of PV can offer.

Unfortunately, however, things are not as cut and dried as the above suggests.Roll-to-roll manufacturing processes--which include, but are not limited to printing—are often touted as a low-cost way to create PV. But this, of course, assumes that these newer approaches work as advertised. It is by no means certain that this is always the case. For example, while, printing and OPV appear to be inseparable, printed inorganic TFPV is not a "done deal." The poster child for printed TFPV (specifically printed CIGS) is Nanosolar, which despite much publicity and a declaration that its new high-capacity factory is operational, has apparently not made any large shipments of its products. Our research suggests that many in the industry believe that printing is not yet yielding the theoretically achievable price performance ratios.

While classic deposition and sputtering techniques may be more expensive than printing in a simplistic sense, the fact that these older approaches are so tried and tested may reduce hidden costs such as training and may lead to improved price performance ratios. PV manufacturers may be willing to pay slightly more for manufacturing equipment that reduces overall manufacturing risk and possibly pushes up the conversion efficiencies at the same time.

Economies of scale: Another way that manufacturing impacts cost is in the form of economies of scale. Two to three years ago economies of scale was not a consideration for TFPV and OPV since firms were either preoccupied with basic chemistry issues or simply didn't see the need for producing large quantities of material; demand for TFPV/OPV had yet to escalate to current levels and production requirements probably did not exceed more than a few MWp in most categories of the market. But they are now and given that basic solar panels are a fairly undifferentiated product, economies of scale may actually be one of the keys to success in the TFPV and OPV space. For example, there is a consensus in the industry that First Solar's success in the TFPV space has been due in no small part to the size of its manufacturing plants.

Perspective #3 Manufacturing and Intellectual Property

Many of the firms with which we have spoken for this report believe that they can increase margins through the use of proprietary manufacturing processes. These are seldom, if ever, completely new approaches, but are much more likely to be variations on a well understood process, although typically firms that stress novel manufacturing approaches will also give a fancy name to how they fabricate cells to enhance the mystique.

Assuming such approaches prove successful, an interesting question is the degree to which they can be formally protected by patents. It should be noted, however, that even where they can't be encapsulated in valuable IP, novel manufacturing approaches for TFPV and OPV may still protect a firm in the marketplace, because it typically takes time to actually get such proprietary approaches up and running and no firm publishes the critical details of how to install or implement such a proprietary approach. So proprietary fabrication approaches are hard to copy, even when there is no legal exposure in doing so.

There is a flip side to all of this though. Any firm adopting its own special approach to TFPV manufacturing must deal with the costs associated with adapting existing machinery to this special approach. These costs include both those associated with having in-house skill sets to carry out this mission and (perhaps) those associated with any additional time required to start up the proprietary process compared with standard approaches in terms of throughput, yield, etc. These extra costs must be measured against the costs of taking more typical routes toward creating PV plants, including the increasingly popular approach of enlisting an equipment manufacturer (or third party) as a systems integrator; the systems integrator opportunity is one that Applied Materials especially has pursued.

Perspective #4 Integrated Approaches to Manufacturing

Integration also seems to be a key issue in manufacturing TFPV and likely to grow in importance in the near future. An integrated approach to manufacturing in TFPV may occur at various levels. At the present time, the most obvious way in which integration can be applied is in combining the workflow for all stages in the TFPV panel approach, with the integration of cell fabrication and metallization being of especial current interest. Although it may add costs in the short term because of the additional costs involved in designing, testing and implementing an integrated plant with significant amounts of in-line processing, there are also considerable efficiencies that can be achieved from this type of plant integration.

There is also an interesting future question about the role of integrated manufacturing in the context of building-integrated PV (BIPV.) Much of this at the present time involves architectural integration; that is, it occurs at the level of building design and construction. However, a growing proportion of BIPV involves actual integrated products, such as solar tiles, shingles and cladding. To achieve maximum manufacturing efficiency, one can imagine fabrication plants of the future that integrate (say) the manufacture of both cladding and the lamination of solar material onto that cladding. Because BIPV is of special interest to suppliers of TFPV and OPV — the flexibility, weight, cost and other factors of TFPV/OPV lend themselves especially well to BIPV — future integrated BIPV fabrication may be of special interest for many of firms reviewed in this report.