Tin Markets for Photovoltaics

Tin is a vital component of the transparent conductive electrodes in thin-film PV (TFPV) cells, but its use is often overshadowed by that of indium, which is much more costly. Tin is used along with indium in indium tin oxide (ITO) and also without indium as tin oxide, which is frequently doped with other materials. ITO has been falling out of favor for TFPV electrodes over the past decade but still accounts for roughly one-third of the market. Tin oxide is one of two major alternative TCOs gaining market share for TFPV electrodes (the other being zinc oxide, similarly doped with other materials). Tin oxide's growing penetration within the TFPV market is mainly due to two factors: a trend of substitution for ITO in amorphous silicon (a-Si) PV and the growth of CdTe PV, which almost universally uses tin oxide.

Growth in the TFPV industry will boost PV-related demand for ITO and tin oxide. However, the high cost of ITO and the high-temperature deposition conditions required for tin oxide will have implications for the long-term growth of these materials in the PV industry, and these implications are discussed in the report. The focus of the report is on the tin used within PV materials. The report begins with a review of the state of the PV industry and then analyzes tin's roles in each of the PV segments. Finally, the report quantifies the opportunities for tin in the PV space through an eight-year forecast.

This report is one of a seven-report series on Metals in PV.

Chapter One: Introduction

1.1 Background to this Report

Rapid growth in the photovoltaic industry has resulted in equally rapid growth in consumption of the materials used for manufacturing PV cells and modules. This, in turn, has led--and will continue to lead--to tremendous opportunities for the suppliers and others involved with these materials, in addition to the device makers themselves. NanoMarkets has been unique in its coverage of both the photovoltaics industry (especially TFPV) and the materials that this industry consumes. In this series of Metals in PV reports, NanoMarkets aims to provide analyses targeted to businesses and investors primarily concerned with specific metals that are used in the photovoltaic industry. For these metals, PV is only part (and usually a relatively small part) of the total market. This report is targeted not only to those already in the photovoltaics business, but also to those in the tin business that are interested in learning about the growth and opportunities available for tin in the photovoltaics industry.

Tin is cheap by photovoltaic materials standards. In an industry that uses silver, indium, tellurium, and germanium--all in comparable quantities to tin--the cost of tin is one drop in a rather large bucket. But tin is a critical part of the photovoltaic devices for which it is used. Primarily, tin is used in the transparent electrodes of thin-film PV cells as either ITO or as doped tin oxides such as fluorine-doped tin oxide (FTO).

The photovoltaic applications of tin, while very small in terms of volume when compared to the other industrial uses of tin, nonetheless represent a rapidly growing use of the metal. One obvious use of tin in PV devices is in ITO, the dominant transparent conductor used by the display industry and others requiring both conductivity and transparency in the same material. The PV industry consumes some of that ITO to form the transparent electrodes on the front (and in some cases also the back) of TFPV cells, and growth in TFPV is driving up the overall volume of ITO consumed by it (although the penetration of ITO into that market is actually falling). ITO has the drawback that it depends on costly indium, and this is a major reason for its decline in penetration in the TFPV market.

But tin oxide is also used without the indium, also to form transparent electrodes. Tin oxide is generally doped with fluorine (FTO), but can also be doped with other materials such as antimony. Aside from its lower cost, FTO can easily be applied directly to glass and is thus often preferred for TFPV cells built in superstrate configuration--where the front electrode is applied directly to a glass substrate, through which light travels (when in use) to enter the cell.

Photovoltaics represents only a tiny portion of tin consumption, and the portion is still small when only tin oxide is considered. Tin oxide is widely used as a coating in other industries because of its conductivity, transparency, and low cost; for instance, tin oxide is used as an antistatic coating on architectural glass. Tin itself has more uses, in much higher volume. It is a major component in bronze and in many solders and other low-melting alloys. It is used in so-called "tin cans" and "tin roofs," which are actually steel coated with tin for its excellent corrosion resistance. Tin is also used to make "float glass" in which flat panes of glass are formed by allowing the glass to harden while floating on a pool of molten tin. There are also various synthetic chemicals that contain tin. These other uses for tin generally lie beyond the scope of this report, although it should be mentioned that float glass is often used as a substrate for TFPV cells.

In one sense, specialty metals are commodities and as such follow traditional supply-demand economics. To this extent, providers focus on competitive advantages in cost, product lines, or service. However, photovoltaics (and especially thin-film photovoltaics) is a high-growth industry, and will drive tremendous growth in demand for the materials used by it, including certain specialty metals. Companies that recognize new or growing opportunities relating to specialty metals in photovoltaics, and capitalize on those opportunities, will stand to benefit ahead of others.

The metals covered in this series are all well-established industrially and have one or more "conventional" uses that account for the bulk of their consumption, but they are also important to certain rapidly-growing PV technologies, which represent a significant growth market. For some of these metals, most notably indium, PV is likely to become one of the largest consumers of them. But even in the case of metals like tin, where PV will only make up a small portion of consumption even under the most optimistic PV growth scenarios, the factors mentioned above will still play out.

While the photovoltaic use of tin oxide and ITO have been covered in the recent NanoMarkets reports "Indium Tin Oxide and Alternative Transparent Conductor Markets," "Materials Markets for Thin-Film and Organic Photovoltaics," and "Indium Markets for Photovoltaics," this report is focused more specifically on the tin. As it will for the other specialty metals covered in this series, photovoltaics will account for a disproportionate amount of the growth in the tin market.