U.S. Department of the Interior

U.S. Geological Survey

Byproduct Mineral Commodities Used 

for the Production of Photovoltaic Cells

Circular 1365
Front cover: A 2-megawatt, ground mounted solar photovoltaic array occupies the site of a former landfill at Fort Carson, Colo. Covering 

nearly 12 acres, the solar photovoltaic array is the largest array located on a U.S. Army facility. Photograph from the U.S. Department of 

Energy Western Area Power Administration (http://www.wapa.gov/newsroom/NewsFeatures/ftcarsonsolar.htm).

Back cover: Installation of flexible thin-film solar panels designed for use on commercial buildings. The panels are made out of thin-film 

solar cells from a combination of copper, indium, gallium, and selenium. Photograph courtesy of SoloPower, Inc., used with permission.
Byproduct Mineral Commodities Used 

for the Production of Photovoltaic Cells

By Donald I. Bleiwas

Circular 1365

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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Suggested citation:

Bleiwas, D.I., 2010, Byproduct mineral commodities used for the production of photovoltaic cells: U.S. Geological 

Survey Circular 1365, 10 p., available at http://pubs.usgs.gov/circ/1365/.
iii

Contents

Introduction.....................................................................................................................................................1

Sources and Supplies of Commodities Used in Photovoltaic Cells .......................................................3

Cadmium .................................................................................................................................................4

Gallium ....................................................................................................................................................5

Germanium .............................................................................................................................................5

Indium .....................................................................................................................................................5

Selenium and Tellurium ........................................................................................................................6

Amounts of Selected Mineral Materials Required for Generating One Gigawatt of Electricity ......6

Summary..........................................................................................................................................................8

References Cited............................................................................................................................................8

Figures

1. Diagram showing the structure of an electricity-generating solar cell ..............................2

2. Diagram illustrating byproduct commodities that affect the efficient operation of 

photovoltaic cells ..........................................................................................................................2

Tables

1. World production from primary sources and price of refined metals for byproduct 

commodities at yearend 2008 .............................................................................................................4

2. Metals required to produce thin-film photovoltaic cells with effective annual 

capacity of 8,760 gigawatthours ................................................................................................7

Conversion Factors

Multiply By To obtain

Mass

kilogram (kg) 2.205 pound avoirdupois (lb)

Byproduct Mineral Commodities Used for the Production 

of Photovoltaic Cells

By Donald I. Bleiwas

1

The amount of power generated during the course of 1 year.

Introduction

Rising fossil fuel costs, environmental concerns relating 

to global climate change, and Government policy to significantly increase our Nation’s energy independence have placed 

greater emphasis on the generation of electricity from renewable sources, such as the Sun (light and heat), water, and wind, 

which for all intents and purposes are inexhaustible resources.

Although the total amount of electricity generated from 

the direct conversion of sunlight through photovoltaic cells 

is relatively small compared with that from other forms of 

renewable energy, the rate of growth in the sector is significant. The total value of energy of photovoltaic cells produced 

worldwide increased to nearly 7 gigawatts (GW) in 2008 from 

45 megawatts (MW) in 1990, a compound annual growth rate 

of about 30 percent. In the United States, manufacturing of 

photovoltaic cells has grown exponentially to about 480 MW 

in 2008, accounting for 6 percent of world production, from 

less than 10 MW of photovoltaic capacity in 1990 (Benner, 

2007; U.S. Department of Energy, Energy Information Administration, 2010), a compound annual growth rate of approximately 23 percent. A production capacity of 1 GW of electricity [or 8,760 gigawatthours1

 (GWh)] is equivalent to the 

annual electricity requirements for roughly 800,000 average 

households in the United States (U.S. Department of Energy, 

Energy Information Administration, 2010). This estimate does 

not include losses of electricity, such as during transmission 

through power lines.

Similarly, China has demonstrated dramatic growth in 

production. In 2004, China contributed about 100 MW of 

photovoltaic cells, about 1 percent of the global total. By 

2008, China’s output had grown to 1.9 GW of photovoltaic 

capacity, about 27 percent of global output (U.S. Department 

of Energy, Energy Information Administration, 2010), a compound annual growth rate of about 80 percent. Other major 

producers of photovoltaic cells in 2008 included Europe (27 

percent of world production), Japan (18 percent), and Taiwan 

(12 percent) (U.S. Department of Energy, 2010).

It should be noted that the increase in production capacity 

as measured in megawatts was probably as much the result of 

the improved efficiency of photovoltaic cells as the increase 

in demand for cells. The United States continued to be the 

leading electricity consuming nation in the world. The U.S. 

Department of Energy estimated that less than 0.02 percent of 

the total electricity generated in the United States in 2008 from 

all other renewable energy sources, including electric, wind, 

wood-burning, biomass, and geothermal sources, originated 

from photovoltaic arrays (U.S. Department of Energy, Energy 

Information Administration, 2010). The major reason for the 

low percentage was the high cost of producing electricity from 

photovoltaic cells compared with that from other established 

sources of electrical power. Wind, which is another renewable 

energy source often used as a comparison point against solar 

generation, produced 50 times the amount produced from solar 

sources (Blansett, 2007). For purposes of perspective, photovoltaic cells are about 7 to 17 percent efficient at converting 

sunlight to electricity, while electricity generated by fossil 

fuels (which produces about 70 percent of U.S. electricity 

generation) is about 28 percent efficient (U.S. Department of 

Energy, Energy Information Administration, 2008b).

Silicon-based photovoltaic cells currently dominate the 

market and are the type most often seen in solar installations 

and on rooftops. They account for more than 90 percent of the 

photovoltaic cells in use and can convert roughly 15 percent of 

the absorbed light to electricity in actual outdoor use. Research 

in recent years has resulted in increased efficiencies and lower 

production costs to the point where second-generation photovoltaic cells known as thin-film cells are making significant 

strides in penetrating the global commercial renewable energy 

market. The efficiency of these cells under laboratory conditions has ranged from about 20 percent to more than 40 percent, depending on composition and design (McMahon, 2008; 

Hecht, 2009; Novak and others, 2009).

Thin-film photovoltaic cells will likely become an important source of electricity generated from sunlight in the future. 

Most thin-film cells have some advantages compared with 

their thicker amorphous silicon cell counterparts (thick-film 

cells). Thin-film cells are lighter because they use much less 

material and can be flexible, making them adaptable to various designs in different applications. The cell’s active area is 

usually only 1 to 10 micrometers (μm) thick. Thick-film cells 

typically are as much as 200 to 400 μm thick (SolarThinFilms, 

2007). Thin-film cells are also more easily manufactured and 
2 Byproduct Mineral Commodities Used for the Production of Photovoltaic Cells

therefore can be mass-manufactured by automated systems 

and are less expensive to produce. However, when compared 

with crystalline silicon cells, thin-film cells are generally less 

efficient at converting sunlight to electricity and may require 

up to twice as much space to produce the same amount of 

electricity. However, the gap is closing with significant progress on improving the output of electricity from thin-film cells 

being reported from laboratory research (U.S. Department of 

Energy, National Renewable Energy Laboratory, 2008). Figure 

1 is a generalized figure of the components that comprise a 

photovoltaic solar cell.

The construction and operation of facilities required for 

the production of electricity generated by “capturing” sunlight, specifically photovoltaic cells, require a diverse mix of 

mineral materials. Photovoltaic cell-based powerplants use 

significant tonnages of mineral materials commonly used for 

structural support and transmission of electricity, including 

aluminum, concrete, copper, glass, nickel, steel, and zinc. 

Land-based reserves and resources (as opposed to resources on 

the sea floor) that contain these materials are widely distributed over a large portion of the Earth’s crust, and any supply 

shortages would likely be short lived when given favorable 

market factors. Silica, the principal raw material used for 

manufacturing the cells, is abundant and readily available, as 

is copper, another major component in some types of cells. 

However, some of the mineral materials currently used in 

more advanced thin-film photovoltaic cells incorporate some 

less common mineral materials that are highly valued for 

the special properties they impart when combined with other 

mineral materials. These characteristics include durability and 

higher levels of light absorption and conversion to electricity 

(Mah, 1998). These mineral materials include cadmium, gallium, germanium, indium, selenium, and tellurium (fig. 2).

p-type semiconductor

n-type semiconductor

Figure 1. A generalized diagram showing the structure of an 

electricity-generating solar (photovoltaic) cell. Semiconductor 

films contain such metals as cadmium, gallium, germanium, 

indium, selenium, and tellurium. The p layer generates a positive 

charge and the n layer generates a negative charge. Front 

and back contacts made up of conductive metals and alloys 

containing aluminum, copper, gold, molybdenum, and silver. 

Diagram courtesy of California Energy Commission, used with 

permission.

Figure 2. Metals such as cadmium, gallium, germanium, 

indium, selenium, and tellurium are recovered as byproducts 

from the production of other metals and are critical to varying 

extents for the efficient operation of photovoltaic cells. The 

current and future supply of some of these metals relies on ores 

mined in many countries and processed to refined metals in 

other countries as well as, to varying degrees, on the recovery 

of the metals as a byproduct of processing primary mineral 

commodities, fly ash produced from coal, and from recycling. 

Photograph of the Earth by the National Aeronautics and Space 

Administration (http://svs.gsfc.nasa.gov/vis/a000000/a000100/

a000155/); phorograph of solar farm by U.S. Department of Energy, 

National Renewable Energy Laboratory (http://www.nrel.gov/data/

pix/Jpegs/13338.jpg).
Sources and Supplies of Commodities Used in Photovoltaic Cells 3

Some examples of the use of these highly valued elements in thin-film photovoltaic cells include copper-indiumgallium-selenide alloy (CIGS), cadmium-tellurium (CdTe), 

and germanium used alone or in combination with other 

elements in the p-type (positive type) and n-type (negative 

type) silicon-based semiconductors in thin-film photovoltaic 

cells (fig. 1). Although these mineral commodities are used in 

relatively small amounts compared with other materials used 

in the manufacture of photovoltaic cells, they play a critical 

role in the performance of thin-film photovoltaic cells. With 

the increasing importance of photovoltaic systems as a source 

of supplying electricity for homes, industrial facilities, and 

supplemental grids in the United States and other countries, 

the demand for these mineral commodities will likely increase 

over the near term. The use of these mineral materials for 

other high-tech applications will also likely increase. There 

are concerns that the availability of mineral materials could 

restrain the rate of growth and the size of the industries that 

use these metals; however, estimates of reserves are temporal 

and expand and contract based on the cost of recovery and 

value (Wilburn and others, 2005).

This report describes the production and sources of 

several mineral commodities contained in thin-film photovoltaic cells that are not widely produced or are produced in 

relatively small quantities as well as general estimates of the 

amounts of the metals required to produce 1 GW. This report 

does not address the geographic distribution and supply of 

components used in the photovoltaic systems that rely on the 

availability of these metals. Investigation into methods of 

recovering materials contained in obsolete photovoltaic cells 

is a relatively new area of research that will likely become 

commercially established as the number of cells available for 

recycling increase. Recycling of these mineral materials is 

already supplementing supply from mining operations (5N 

Plus, 2010).

Sources and Supplies of Commodities 

Used in Photovoltaic Cells

The adequacy of the supply of cadmium, gallium, germanium, indium, selenium, and tellurium, all of which are produced 

as byproducts from the production of other metals, is critically 

important for the implementation of large-scale global photovoltaic systems using current technologies. The supply of these commodities relies to a great extent on mining ores for the production of aluminum, coal, copper, and zinc. Considering historical 

prices, it would be unlikely that production of the primary products would increase in order to produce more of the six metals 

discussed in this report. For example, it is unlikely that more coal 

will be mined and burned in order to recover more germanium 

from ash, nor is it likely that more copper ore would be extracted 

to recover tellurium and more bauxite mined to recover more 

gallium during the production of alumina.

Supplies for most of these byproduct metals recovered 

from mining could potentially be increased as a result of a 

number of separate and related scenarios, including:

• the supply of the primary revenue-producing commodities increases as a result of an increase in the value of 

the metals

• new government policies are created to provide incentives for production

• byproduct metal prices increase, justifying increased 

production from mines and processing plants that currently produce the metals (increased production can 

be attained from expansion of existing facilities and 

construction of new circuits to recover the metals from 

sites where the metals are not currently produced but 

are potentially recoverable)

• technologies of metallurgical recovery improve

• supplies from deposits not currently producing the metals discussed can be recovered, such as new deposits 

discovered, past producers, and treatment of residual 

mine and processing waste

• the byproduct commodities are substituted with other 

materials and 

• recycling rates of the byproduct commodities improve

Additional production might also be generated from sources 

where cost is not the highest priority; for example, an enterprise may be willing to contract for a guaranteed supply of 

metals to ensure long-term availability or a facility that is 

vertically integrated is able to recover the higher costs for the 

metals in a value-added product, such as a photovoltaic cell.

Alternatively, an increase in the price of the metal commodity, perhaps coupled with concerns about the adequacy of 

supply for large-scale implementation of photovoltaic technology and applications and technologies competing for the same 

materials, could provide incentive to investigate substitution 

by other materials. This in turn could produce other technological advances [such as dematerialization (using less to 

provide the same or greater results)] that could result in a shift 

in demand to other commodities or using less material with 

the same or improved performance or some yet undiscovered 

technology. More efficient cells (achieving the same or more 

power for less cost) could result in changes in materials use. 

Sudden changes in material use patterns can also occur, such 

as wartime materiel production of scientific breakthroughs 

creating revolutionary changes in materials use.

Table 1 lists the estimated world refined primary production for each of the byproduct metals discussed in this report, 

the primary mining industry from which most of the byproducts are recovered, and the average price for the byproduct 

commodity. A brief discussion of each byproduct metal shown 

in table 1 follows.
4 Byproduct Mineral Commodities Used for the Production of Photovoltaic Cells

Table 1. World production from primary sources and price of 

refined metals for byproduct commodities at yearend 2008.

[e, estimated]

Price of refined World refinery Byproduct com- Primary1 metale,2

productione

modity commodities (in dollars per (in metric tons) kilogram)

Cadmium Zinc 3,4 16,000 6

Gallium Aluminum, zinc 3 111 570

Germanium Zinc, coal5 6 140 1,490

3 Indium Zinc 570 685

3,7 Selenium Copper 3,000–3,500 71

Tellurium Copper 450–500 211

1

Derived as a product of mining ore for the purpose of extracting the listed 

commodity. Secondary production refers to the recovery of metals from the 

recycling of materials following useful service.

2

Rounded to three significant figures. Data are from U.S. Geological Survey 

(2009a,b, 2010).

3

Prices for cadmium, indium, selenium, and tellurium are averages for 

2008. Prices for gallium and germanium, are yearend 2008. All prices rounded 

to the nearest dollar and are reported in dollars per kilogram. Data are from 

U.S. Geological Survey (2009a,b, 2010). Prices may vary based on numerous 

factors that include contractual agreements, size of inventories, and specifications of the metals traded.

4

An additional supply equal to about 25 percent of primary refined cadmium 

production (about 4,000 metric tons) originated from recycling.

5

Recovered from fly ash, a byproduct of coal combustion for energy production.

6

Price for polycrystalline zone-refined germanium; does not represent the 

unit value of entire world production. Data are from Guberman (2010).

7

Does not include U.S. production.

Cadmium

Nearly all the world’s primary (recovered from mining) 

cadmium is derived as a byproduct of processing sphalerite, 

a zinc sulfide ore containing varying amounts of cadmium, 

indium, lead, and other recoverable or potentially recoverable metals. Zinc ores containing cadmium are mined in many 

countries. The three leading producers of cadmium contained 

in ore in 2008, in descending order of quantity produced, were 

China, Peru, and Australia (Tolcin, 2010a).

Like many other commodities, the refined cadmium is 

smelted in countries other than the producing country. In 2008, 

the major producing countries of refined cadmium recovered 

from primary sources (and their approximated percentage shares 

of the world total) included China, where cadmium was refined 

from domestic and imported zinc concentrates (22 percent); the 

Republic of Korea, where virtually all cadmium was derived 

from imported zinc concentrates (15 percent); Japan, where 

cadmium was recovered from imported sources (11 percent); 

Kazakhstan, where cadmium was refined mostly from domestic 

sources (10 percent); and Canada, where cadmium was recovered from domestic, United States, and South American zinc 

concentrates (7 percent) (Tolcin, 2009a).

The United States has the capacity to recover primary 

cadmium from domestic zinc operations. In 2009, most of the 

Nation’s zinc mines and refining facilities were on standby 

status because of low metal prices. Significant amounts of 

cadmium were not produced in 2008 owing to a reduction in 

zinc production worldwide. For example, cadmium production 

in the United States was about one-half the amount produced 

early in the decade. Although the actual amount is not known, 

a substantial amount (probably in the thousands of tons) of 

cadmium is not recovered worldwide and is contained in processing waste and disposed at impoundment areas because of 

the relatively low price of the metal.

Approximately 19,600 metric tons (t) of refined primary 

cadmium was produced worldwide in 2008, of which about 20 

percent, or roughly 4,000 t, was produced through recycling 

(Tolcin, 2009a, 2010a). Total refined production of cadmium 

from primary and secondary sources has remained relatively 

steady over the decade, although the share originating from 

primary cadmium has probably decreased (Wilburn, 2007). 

The decrease in supply from mining resulted primarily from 

an increase in the supply of secondary cadmium recovered 

from recycling of obsolete nickel-cadmium (NiCd) batteries 

coupled with decreased use of NiCd batteries because of technological advances in batteries that use other materials, such 

as lithium-ion and magnesium; primary cadium production has 

also decreased because of overall decreased demand for metals 

owing to depressed global economic conditions, and concerns 

associated with the metal’s potentially toxic effects on the 

environment and human health.

Approximately 20 percent of the global supply of cadmium in 2008 originated from recycled NiCd batteries, with 

additional amounts supplied from other materials containing cadmium. In 2008, about 80 percent of global cadmium 

consumption was in NiCd batteries (Tolcin, 2009a). The 

supply of cadmium introduced from the recycling of obsolete 

consumer-type rechargeable NiCd batteries has been increasing and should continue to increase for some years because 

NiCd batteries for many consumer uses are still favored in 

low-cost consumer products. However, with improved battery 

technologies and concerns for the environment, the amount 

of cadmium used for the production of NiCd type batteries is 

declining (Wilburn, 2007). Industrial-sized NiCd batteries are 

widely used and may find application in storage for electricity 

produced by photovoltaic systems and from other renewable 

forms of energy production. This use could result in reversing a decline in NiCd-battery use in consumer products in 

the future. Although some environmental concerns have been 

raised regarding the use of cadmium in photovoltaic cells, it is 

unclear how these concerns might ultimately affect the use of 

the metal. However, the issue will likely result in placing more 

emphasis on ensuring recycling of photovoltaic cells.

Considering the important role that zinc plays in society 

and the supply of cadmium recovered through recycling, it 

is not anticipated that the metal will become unavailable for 

more than short durations.
Sources and Supplies of Commodities Used in Photovoltaic Cells 5

Gallium

Almost all the world’s primary gallium supply originates as 

an impure byproduct recovered during the processing of bauxite 

ore to alumina, a precursor to refined aluminum. Minor amounts 

of gallium are also recovered from residues produced during the 

process to recover primary zinc metal. In 2008, approximately 

111 t of primary refined gallium was produced worldwide, about 

30 percent below reported capacity (Jaskula, 2010). Some of the 

impure gallium product is refined onsite, but much of it is sold 

and processed into gallium metal of differing purities elsewhere. 

China, Germany, and Kazakhastan are the leading producers 

of impure gallium. They compose roughly 50 percent of world 

primary production. Other major producers, in decreasing order 

of quantity produced, include Japan and Russia. The leading 

purchasers and producers of refined gallium include China, Japan, 

and the United States.

The amount of potentially recoverable gallium is much 

larger than that actually recovered owing to limited demand for 

the metal. Most of the gallium contained in bauxite ore is actually disposed as waste from the processing of ore to alumina. 

An increase in gallium demand beyond current capacity can be 

easily satisfied with the addition or expansion of recovery circuits 

at existing alumina facilities. It is unlikely that the future supply 

of gallium will be constrained because of limited aluminum production. Very little gallium is recovered from recycled obsolete 

materials.

Gallium finds its greatest application in electronic circuitry, 

laser diodes, and light emitting diodes (LEDs) (Kelly and Matos, 

2006; Matos, 2006). Photovoltaic cells that incorporate gallium 

arsenide are mostly used for generating electricity for satellites 

and space exploration. Although gallium arsenide is well suited 

to photovoltaic cells, its application for consumer use is greatly 

limited by the high cost of producing gallium arsenide crystals, a 

necessary component of the cell. Lowering the cost of production 

will likely be key to commericialization of the technology. 

Germanium

Approximately 140 t of primary germanium metal in 

various forms was produced in 2008, of which roughly 60 percent was recovered from residues generated during the production 

of refined zinc derived from ores, and about 30 percent originated from leaching fly ash, a waste product of coal combustion 

(David Guberman, mineral commodity specialist, U.S. Geological Survey, oral commun., April 19, 2010). The vast majority of 

germanium production originated from China (a mix of domestic 

and imported feedstock) and Canada (mostly North American 

in origin). Other countries with notable germanium production 

include Belgium (all derived from imported feedstock), Russia (mostly domestic in origin), and the United States (a mix of 

domestic and imported).

In 2007, germanium metal was in short supply owing to 

a reduction in zinc production, which was caused by low metal 

prices that resulted from depressed demand and increased demand 

for germanium for use in fiber optics and infrared technologies 

(Matos, 2006; Guberman, 2009, 2010). This supply shortage was 

reflected in the price of germanium, which increased by nearly 

30 percent to $1,240 per kilogram for zone-refined germanium at 

yearend 2007 from about $950 per kilogram at the beginning of 

the year (Guberman, 2010). In 2008, the price of the metal continued to rise, and yearend 2008, was $1,490 per kilogram. Primary 

germanium supply relies to some extent on zinc production, 

which is currently operating significantly below capacity. More 

germanium could potentially become available with the improvement of the zinc market. The amount of germanium potentially 

recoverable from coal fly ash is essentially unlimited (Simons 

and Prinz, 1973a), but the commercial recovery of the metal is 

not currently viable to the extent that it has replaced germanium 

recovered from primary sources. The amount of germanium 

recovered from recycling efforts is not a significant contributor to 

world supply of germanium.

Indium

Approximately 570 t of indium was produced from 

primary sources in 2008 (Tolcin, 2010b). Most of the world’s 

primary indium supply originates as a byproduct of processing 

zinc ores mined in China, Peru, and Australia (in decreasing 

order of quantity produced). Another source of primary indium 

supply is mines of other types of metals, mostly copper, lead, 

tin, and precious metals. As with many metals, the smelting 

and refining of concentrates take place in countries other than 

where the ore is mined. Like cadmium, most of the world’s 

indium supply originates from zinc mining. The majority of 

smelting and refining of indium takes place in Canada, China, 

Japan, and the Republic of Korea. China recovers nearly 55 

percent of the world’s refined indium from mostly domestic 

sources. The Republic of Korea (mostly from imported concentrates), Japan (from imported concentrates), and Canada 

(from mostly domestic and U.S. sources) account for about 

13, 11, and 8 percent of the world’s primary refined indium 

production, respectively (Tolcin, 2009b, 2010b).

Flat-panel liquid crystal displays (LCDs) for computer 

monitors and flat-screen televisions are the leading application 

for indium (as an alloy consisting of indium tin oxide), consuming more than 50 percent of the world primary output of 

indium, and will likely continue to dominate the use of the element for the foreseeable future. Nearly all indium reclaimed 

from manufacturing of electronics, including LCDs, is also 

used for producing flat-panel displays (Matos, 2006; Mikolajczak, 2009). Photovoltaic cells and other competing uses may 

increase demand for indium. Expansions of existing recovery 

circuits and installations of new primary recovery circuits 

with improved recoveries are coming online, exploration of 

deposits containing anomalously high amounts of indium have 

become more attractive for potential development, and the 

recovery of indium from processing wastes (tailings and slags) 

is now being practiced on a limited scale and could become a 
6 Byproduct Mineral Commodities Used for the Production of Photovoltaic Cells

significant source of future indium supply if demand justifies 

investment. More efficient production methods using indium 

tin oxide and improved technology to reclaim metals collected 

from the production of LCDs and other products are also being 

researched (Mikolajczak, 2009).

Although not currently a major source of indium, a potentially significant secondary indium industry with a focus on 

recycling electronic waste is likely to emerge under favorable 

market conditions and will potentially play a role in supplementing world indium supply as the metal finds use in other 

applications.

As with cadmium, the largest percentage of indium 

production relies on mining zinc ores. It is anticipated that the 

supply of indium will be able to meet anticipated industrial 

demand. Gallium may also potentially serve as a substitute for 

indium in some applications, including photovoltaic cells, if 

there are cost benefits (Andersson, 2000).

Selenium and Tellurium

In 2008, approximately 3,000 to 3,500 t of refined 

selenium and 450 to 500 t of refined tellurium were produced as a result of mining and processing ores derived from 

primary sources (George, 2009). Japan and Belgium are 

the leading producers of these metals, which are recovered 

from copper concentrates and residues purchased primarily 

from mining operations in Africa, Asia, Australia, and South 

America. China is also a large purchaser from these regions 

and also produces the metals from domestic mining operations. Although some of the selenium and tellurium metal is 

recovered from some gold and silver deposits with anomalously high levels of selenium and tellurium content, nearly all 

the world’s selenium and tellurium metal produced from ore 

deposits depends on profitable recovery from residues (slimes) 

produced during the refining of copper to copper cathode; this 

copper cathode is derived from the mining of copper sulfide 

ore, from some polymetallic ore bodies (for example, the 

Sudbury nickel district), and from lead and zinc operations 

(Simons and Prinz, 1973b,c). The content of each selenium 

and tellurium metal in copper concentrate is generally below 

100 parts per million each. The metals are commercially profitable to recover only when they are concentrated in residues 

collected from copper refineries and treated for the recovery 

of metals of value, which generally include antimony and precious metals, such as gold, palladium, platinum, and silver.

It was also estimated that, approximately 4,600 t could 

have been potentially recovered from copper anode slimes 

in 2008 (George, 2009). Mining operations that leach copper 

from ores do not produce anode slimes, and therefore none of 

the selenium or tellurium contained in the ores is recovered 

(Simons and Prinz, 1973b,c). Relatively small amounts of 

the two metals are also recovered from residues generated 

during the processes necessary to produce gold, lead, and 

zinc. Overall, roughly 50 to 60 percent of the selenium and 

tellurium contained in ore is refined to metal. The balance 

is contained in waste products, such as mill tailings, and in 

slag (Ojebuoboh, 2007). Because of expectations of increasing demand and higher prices for selenium metal, there is an 

increased focus on exploration for deposits containing selenium, which at one time was considered a deleterious component in ores, as well as tellurium. Significant improvements 

in recovery of selenium and tellurium at refineries will likely 

result in an increase in supply of selenium if prices justify 

recovery.

Using broad assumptions, a U.S. Department of Energy, 

National Renewable Energy Laboratory (2000) study estimated that approximately 900 t of copper sulfide ore extracted 

from copper porphyry deposits, the largest source of world 

primary copper, is required to recover 1 pound of byproduct 

tellurium and that at least 1,000 t of byproduct tellurium, or 

roughly ten times the world production in 2008, could potentially be produced annually from mining operations; however, 

for a number of reasons, chief among them being economics and proprietary technologies, the metal is not recovered 

at this time. This estimate is relatively close to the 1,200 t of 

tellurium potentially recoverable from copper anode slimes 

(George, 2009). An earlier study stated that approximately 0.4 

pound of tellurium was contained in 2,000 pounds of blister 

copper, of which approximately 43 percent of the metal was 

potentially recoverable (Simons and Prinz, 1973c). The difference in the estimated recoverable amounts in the studies can 

be attributed to technological advances that have resulted in 

significant improvements in metallurgical recoveries since the 

early study was published.

The high price of tellurium and the anticipated increased 

demand for the metal have brought attention to a number of 

mineral deposits found to contain high tellurium contents that 

are being considered for development in China and Mexico. 

As is also typical with sustained higher commodity prices and 

(or) anticipated increased demand, efforts are concentrated 

more on research for improved recoveries from ores and 

investigations into processing the waste materials generated by 

producing and past mines and processing plants for potential 

recovery of the metals. These activities will likely result in 

an increase in supply of the metals when prices justify their 

recovery.

Only small amounts of selenium and tellurium metal are 

recovered by recycling obsolete materials.

Amounts of Selected Mineral 

Materials Required for Generating 

One Gigawatt of Electricity

Table 2 provides rough estimates of the amounts of the 

six byproduct mineral materials used in two types of thin-film 

photovoltaic cells sufficient to produce 8,760 GWh annually with 

a peak capacity of 4 GW of electricity production and an effective 

average daily capacity of 1 GW, based on a 25 percent capacity 

factor, which accounts for the hours of daylight and other factors 

affecting electricity production.
Amounts of Selected Mineral Materials Required for Generating One Gigawatt of Electricity 7

Depending on the type, efficiency of cells employed, and a 

number of other factors, a total surface area of roughly 40 square 

kilometers (nearly 15 square miles) of photovoltaic panels could 

be required to produce this amount of electricity assuming a peak 

wattage output of 110 watts per square meter. The area required 

to accommodate other necessary parts of generating plants is 

not included in this estimate. An area of roughly 33,000 square 

kilometers (13,000 square miles) might be required to meet the 

electricity needs of the United States using only photovoltaic cells 

(New Mexico Solar Energy Association, 1999). This is not to suggest that a single plant would be required to occupy this amount 

of area for the production of the electrical energy; rather it would 

likely require a significant number of plants distributed throughout the United States. For perspective, the largest operating photovoltaic plant in the world is the Parque Fotovoltaico Olmedilla 

de Alarcon solar farm in Spain which is designed to produce 

about 60 MW at peak levels. In California, the proposed 550MW 

Topaz Solar Farm Project is planned to produce nearly 1.1 GWh 

using thin-film CdTe photovoltaic cells when it becomes fully 

operational in 2013 (Pacific Gas and Electric Company, 2008). If 

the plant’s construction follows the original design, the plant will 

be the world’s largest, encompassing an area of about 25 square 

kilometers (9.5 square miles) (Hudson, 2008; Rigley, 2009).

The estimates presented in table 2 provide a perspective for 

selected material requirements in three types of photovoltaic cells 

used mostly for commercial purposes. Other types of photovoltaic cells, such as gallium-arsenide- and germanium-based cells, 

are mainly reserved for use in satellites and space exploration 

because of their high efficiencies. They are much more expensive 

compared to most other types of cells in use and not economically 

practical for large-scale commercial application, but research is 

ongoing. The estimates in table 2 should be considered to be a 

“snapshot” because advances in the field of photovoltaic technology that require different amounts and types of materials are 

announced frequently. Actual material requirements could differ 

significantly from the estimates because cell types are generic 

categories and do not have a standardized composition. Within 

cell types, the amounts and selections of materials used and their 

structure vary. In addition, information about characteristics of 

cells is usually considered proprietary and therefore is difficult to 

acquire. The amount of electricity produced from photovoltaic 

cells of the same composition and type will differ in practice 

because of numerous criteria that include the design of the array 

(fixed-position or tracking), geographic location, including altitude and latitude (determines the number of hours and the angle 

of sunlight), and prevailing climatic conditions, primarily cloud 

cover during daylight hours. These factors result in an electricity 

production efficiency factor that can vary from 15 to 35 percent 

of production under optimum (peak) conditions. The calculations 

in table 2 use an assumed capacity factor of 25 percent (estimates 

range from about 20 to 30 percent for the 48 contiguous United 

States). For these reasons, material requirements and electrical 

power production are most often standardized under ideal circumstances and as peak power per panel or as electricity produced by 

photovoltaic panel surface area at peak power. A capacity factor is 

applied for planning and construction purposes.

Table 2. Metals required1 to produce thin-film photovoltaic cells with effective annual capacity of 8,760 gigawatthours.

[CIGS, copper-indium-gallium-selenide alloy; e, estimated; XX, not applicable]

Type of photovoltaic technology

Metals required

Metal Quantitye,2

(metric tons)

Percentage of 2008 estimated 

world refinery production from 

primary sources3

Value of contained metale,4

(in millions of dollars) 

Thin-film CIGS

Thin-film cadmium telluride

Gallium

Indium

Selenium

Total

Cadmium

Tellurium

Total

30

90

180

XX

340

390

XX

27

16

6

XX

2

82

XX

17

62

13

92

 2

82

84

1

Metals required to produce photovoltaic cells that can generate 4 gigawatts (GW) of peak power or 8,760 gigawatthours per year (GWh/yr) of effective 

capacity. One GW is equivalent to 1 billion watts, 1,000 megawatts, and 1 million kilowatts of effective capacity of electricity production. Applying a 25 percent 

capacity factor, an installed peak capacity of approximately 4 GW would be required to produce 1 GW of electricity on an average daily basis or 8,760 GWh/yr, 

electricity sufficient to meet the average annual need of 11,000 kilowatthours for 800,000 households in the United States (U.S. Department of Energy, Energy 

Information Administration, 2009a). No energy storage, such as batteries, was assumed.

2

Calculation for metal requirements assumed to be linear and based on a 3-micrometer (μm) thickness cell. Two-μm thickness cells are in development and 

are expected to penetrate the commercial market within the next several years. The combination, amounts, and efficiency of materials used in photovoltaic cells 

can vary; the amounts and combinations listed in this table are not representative of all technologies. Estimates for material requirements should be considered 

with caution. The amount of material required (the size of the array) to produce a given amount of energy can vary greatly by the physical location of photovoltaic arrays that affect insolation (such as latitude and weather conditions) and design factors (such as the type of cells and whether the system is fixed tilt or 

tracking). Estimates are based on a 25 percent capacity factor. Values are rounded to two significant figures.

3

Rounded to two significant figures.

4

Rounded to two significant figures. Prices for cadmium, indium, selenium, and tellurium are average 2008; prices for gallium and germanium are yearend 

2008. All prices are rounded to the nearest dollar and are reported in dollars per kilogram. Data are from U.S. Geological Survey (2009a,b, 2010). Prices may 

vary based on numerous factors that include contractual agreements, size of inventories, and specifications of the metals traded.
8 Byproduct Mineral Commodities Used for the Production of Photovoltaic Cells

Summary

Metals such as cadmium, gallium, germanium, indium, 

selenium, and tellurium are important mineral materials used 

in current photovoltaic cell technology. Most of the world’s 

primary supply of these mineral commodities is recovered 

as byproducts from ores processed mainly for the purpose of 

producing aluminum, copper, lead, and zinc and, in the case 

of germanium, from ash derived from burning coal for the 

production of energy. In some cases, the refined metals originate 

in the countries in which they are mined, while in other cases, 

intermediate products containing the metals and refined metals 

are recovered by processers located in other countries. Assuming that the modest rate of market penetration of electricity from 

photovoltaic cells and competing markets increases demand for 

cadmium, gallium, and germanium, the resulting new demand 

can be met in relatively quick order with the expansion of 

existing recovery circuits or the addition of new circuits. It is 

very unlikely that, under most scenarios, the need would arise 

to mine more bauxite, copper, and zinc ore or to burn more 

coal to satisfy anticipated material requirements to meet the 

photovoltaic-generated demand for these mineral materials. For 

other metals, such as indium, selenium, and tellurium, targeted 

mineral exploration and improvements in metallurgical recoveries are likely to be needed to meet demand requirements. Substitution for these materials in nonphotovoltaic applications could 

also “free up” supply. Conversely, however, other new applications can produce supply constraints or increase metal prices 

and place pressure on their use in photovoltaic technology.

The supply of these metals from secondary sources will 

likely increase over time when photovoltaic cells are recycled 

as a result of breakage or when they reach the end of their useful life of approximately 20 to perhaps 30 years (U.S. Department of Energy, Solar Technologies Program, 2008a).

Other than perhaps short term interruptions resulting 

from market forces or geopolitical events, it is not anticipated that there will be any long term material constraints 

that would prevent the development of a significant amount 

of energy from photoelectric cells. Reserve estimates are not 

static; although a particular metal might be considered rare 

and scarce, if a profit can be made from its recovery, then there 

will likely be no long-term shortage. Technological advancements driven by the desire to produce energy at a lower cost 

will likely result in increases in efficiency requiring smaller 

amounts of these metals per unit of energy produced, substitution with other materials, and other advancements in science.

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Bleiwas—Byproduct Mineral Commodities Used for the Production of Photovoltaic Cells—Circular 1365

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