Third-generation photovoltaic cell

'''Third-generation photovoltaic cells''' are [[solar cell]]s that are potentially able to overcome the [[Shockley–Queisser limit]] of 31–41% power efficiency for single [[bandgap]] solar cells. This includes a range of alternatives to cells made of semiconducting [[p–n junction]]s ("first generation") and [[thin-film solar cell|thin-film cells]] ("second generation"). Common third-generation systems include multi-layer ("tandem") cells made of [[amorphous silicon]] or [[gallium arsenide]], while more theoretical developments include frequency conversion, (i.e. changing the frequencies of light that the cell cannot use to light frequencies that the cell can use – thus producing more power), hot-carrier effects and other multiple-carrier ejection techniques.<ref>{{Cite journal | doi = 10.1063/1.1736034| title = Detailed Balance Limit of Efficiency of p–n Junction Solar Cells| journal = Journal of Applied Physics| volume = 32| issue = 3| pages = 510| year = 1961| last1 = Shockley | first1 = W. | last2 = Queisser | first2 = H. J. | bibcode = 1961JAP....32..510S}}</ref><ref>{{Cite book|last1=Luque|first1=Antonio|url=https://books.google.com/books?id=mPJSAAAAMAAJ|title=Physical Limitations to Photovoltaic Energy Conversion|last2=López Araujo|first2=Gerardo|publisher=Adam Hilger|year=1990|isbn=0-7503-0030-2|location=Bristol}}</ref><ref>{{Cite journal | doi = 10.1002/pip.360| title = Third generation photovoltaics: Ultra-high conversion efficiency at low cost| journal = Progress in Photovoltaics: Research and Applications| volume = 9| issue = 2| pages = 123–135| year = 2001| last1 = Green | first1 = M. A. }}</ref><ref name="MartíLuque2003">{{cite book|first1=A. |last1=Martí|first2=A. |last2=Luque|title=Next Generation Photovoltaics: High Efficiency through Full Spectrum Utilization|url={{google books |plainurl=y |id=xHt1HBp_qKgC}}|date=1 September 2003|publisher=CRC Press|isbn=978-1-4200-3386-1}}</ref><ref>{{Cite journal | doi = 10.1016/S1369-7021(07)70278-X| title = Third-generation photovoltaics| journal = Materials Today| volume = 10| issue = 11| pages = 42–50| year = 2007| last1 = Conibeer | first1 = G. | doi-access = free}}</ref>

Emerging photovoltaics include: * [[Copper zinc tin sulfide]] solar cell (CZTS), and derivates CZTSe and CZTSSe * [[Dye-sensitized solar cell]], also known as "Grätzel cell" * [[Organic solar cell]] * [[Perovskite solar cell]] * [[Quantum dot solar cell]]

Perovskite cells, in particular, have received attention as their research efficiencies rose above 20 percent. They also offer a wide variety of low-cost applications.{{Clarify|date=March 2026|reason=what applications do pvs have besides electricity?}}<ref> {{cite web |url=http://phys.org/news/2014-07-stable-cost-cutting-perovskite-solar-cell.html |title=A new stable and cost-cutting type of perovskite solar cell |work=PHYS.org |date=17 July 2014 |access-date=4 August 2015 }}</ref><ref>{{cite web |url=http://www.rsc.org/chemistryworld/2014/07/perovskite-solar-cell-scalable-manufacturing-spray-deposition |title=Spray-deposition steers perovskite solar cells towards commercialisation |work=ChemistryWorld |date=29 July 2014 |access-date=4 August 2015 }}</ref><ref>{{cite web |url=http://www.ossila.com/support/industry_news/Perovskites_and_perovskite_solar_cells.php |title=Perovskite Solar Cells |work=Ossila |access-date=4 August 2015 }}</ref> In addition, another emerging technology, [[concentrator photovoltaics]] (CPV), uses high-efficient, [[multi-junction solar cell]]s in combination with optical lenses and a tracking system.

== Technologies == Solar cells can be thought of as [[visible light]] counterparts to [[radio receiver]]s. A receiver consists of three basic parts; an antenna that converts the radio waves (light) into wave-like motions of [[electron]]s in the antenna material, an electronic valve that traps the electrons as they pop off the end of the antenna, and a tuner that amplifies electrons of a selected frequency. It is possible to build a solar cell identical to a radio, a system known as an [[optical rectenna]], but to date these have not been practical.

The majority of the solar electric market is made up of silicon-based devices. In silicon cells, the silicon acts as both the antenna (or [[electron donor]], technically) as well as the electron valve. Silicon is widely available, relatively inexpensive and has a bandgap that is ideal for solar collection. On the downside it is energetically and economically expensive to produce silicon in bulk, and great efforts have been made to reduce the amount required. Moreover, it is mechanically fragile, which typically requires a sheet of strong glass to be used as mechanical support and protection from the elements. The glass alone is a significant portion of the cost of a typical solar module.

According to the Shockley–Queisser limit, the majority of a cell's theoretical efficiency is due to the difference in energy between the bandgap and solar photon. Any photon with more energy than the bandgap can cause photoexcitation, but any energy above the bandgap energy is lost. Consider the solar spectrum; only a small portion of the light reaching the ground is blue, but those photons have three times the energy of red light. Silicon's bandgap is 1.1 eV, about that of red light, so in this case blue light's energy is lost in a silicon cell. If the bandgap is tuned higher, say to blue, that energy is now captured, but only at the cost of rejecting lower energy photons.

It is possible to greatly improve on a single-junction cell by stacking thin layers of material with varying bandgaps on top of each other – [[Multijunction photovoltaic cell|the "tandem cell" or "multi-junction"]] approach. Traditional silicon preparation methods do not lend themselves to this approach. Thin-films of amorphous silicon have been employed instead, notably [[Energy Conversion Devices|Uni-Solar]]'s products, but other issues have prevented these from matching the performance of traditional cells. Most tandem-cell structures are based on higher performance semiconductors, notably [[gallium arsenide]] (GaAs). Three-layer GaAs cells achieved 41.6% efficiency for experimental examples.<ref>David Biello, [http://www.scientificamerican.com/blog/post.cfm?id=new-solar-cell-efficiency-record-se-2009-08-27 "New solar-cell efficiency record set"], ''Scientific American'', 27 August 2009</ref> In September 2013, a four layer cell reached 44.7 percent efficiency.<ref>{{cite web | title=Solar cell hits new world record with 44.7 percent efficiency| url=http://www.treehugger.com/solar-technology/solar-cell-hits-new-world-record.html | access-date=26 September 2013}}</ref>

Numerical analysis shows that the "perfect" single-layer solar cell should have a bandgap of 1.13 eV, almost exactly that of silicon. Such a cell can have a maximum theoretical power conversion efficiency of 33.7% – the solar power below red (in the infrared) is lost, and the extra energy of the higher colors is also lost. For a two layer cell, one layer should be tuned to 1.64 eV and the other at 0.94 eV, with a theoretical performance of 44%. A three-layer cell should be tuned to 1.83, 1.16 and 0.71 eV, with an efficiency of 48%. A theoretical "infinity-layer" cell would have a theoretical efficiency of 68.2% for diffuse light.<ref>{{cite book|last1=Green|first1=Martin|title=Third generation photovoltaics|date=2006|publisher=Springer|location=New York|page=66}}</ref>

While the new solar technologies that have been discovered center around nanotechnology, there are several different material methods currently used.

The third generation label encompasses multiple technologies, though it includes non-[[semiconductor]] technologies (including [[polymer]]s and [[biomimetics]]), [[Quantum dot solar cell|quantum dot]], [[Multijunction photovoltaic cell|tandem/multi-junction cells]], [[Intermediate band photovoltaics|intermediate band solar cell]],<ref>{{Cite journal|last1=Luque|first1=Antonio|last2=Martí|first2=Antonio|title=Increasing the Efficiency of Ideal Solar Cells by Photon Induced Transitions at Intermediate Levels|url=https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.78.5014|journal=Physical Review Letters|year=1997|volume=78|issue=26|pages=5014–5017|doi=10.1103/PhysRevLett.78.5014|url-access=subscription}}</ref><ref>{{cite journal|author1=Weiming Wang |author2=Albert S. Lin |author3=Jamie D. Phillips |title=Intermediate band photovoltaic solar cell based on ZnTe:O |journal=Appl. Phys. Lett.|volume=95 |issue=1 | page =011103 |year=2009 |doi=10.1063/1.3166863|bibcode=2009ApPhL..95a1103W }}</ref> [[hot-carrier cell]]s, [[photon upconversion]] and [[wikt:downconversion|downconversion]] technologies, and [[solar thermal]] technologies, such as [[thermophotonics]], which is one technology identified by Green as being third generation.<ref>{{cite book | last = Green | first = Martin | title = Third Generation Photovoltaics: Advanced Solar Energy Conversion | publisher = [[Springer Science+Business Media]] | year = 2003 | isbn = 978-3-540-40137-7 }}</ref>

It also includes:<ref>{{cite web | author = UNSW School for Photovoltaic Engineering | title = Third Generation Photovoltaics | url = http://www.pv.unsw.edu.au/Research/3gp.asp | access-date = 2008-06-20}}</ref>

* [[Silicon nanostructure]]s * Modifying incident spectrum ([[concentrator photovoltaics]]), to reach 300–500 suns and efficiencies of 32% (already attained in Sol3g cells<ref>[https://guntherportfolio.blogspot.com/2007/07/sol3g-secures-triple-junction-solar.html Sol3g secures Triple Junction Solar Cells from Azur Space]</ref>) to +50%. * Use of excess thermal generation (caused by [[UV light]]) to enhance voltages or carrier collection. * Use of [[infrared]] spectrum to produce electricity at night.

== See also == {{Portal|Renewable energy|Energy}} *[[Band gap]] *[[Nanoantenna]] *[[Organic electronics]] *[[Printed electronics]]

== References == {{Reflist|2}}

== External links == * [https://web.archive.org/web/20090125210629/http://org.ntnu.no/solarcells/pages/generations.php Different generations of solar cells] * [http://www.phys.vt.edu/~rheflin/ Research] in [[Virginia Tech]] * [http://www.renewableenergyworld.com/rea/news/article/2009/05/solar-shootout-in-the-san-joaquin-valley Solar Shootout in the San Joaquin Valley] * [http://news.cnet.com/Silicon+vs.+CIGS+With+solar+energy,+the+issue+is+material/2100-1008_3-6121488.html Silicon vs. CIGS: With solar energy, the issue is material] * [http://optics.org/cws/article/research/23961 Start-up targets thin-film silicon solar cells] * [http://light.utoronto.ca/tsargent/pdfs/article-nationalgeographic-14jan2005.pdf Spray-On Solar-Power Cells Are True Breakthrough] * [http://light.utoronto.ca/tsargent/pdfs/article-businessweek-31jan2005.pdf Solar Cells: The New Light Fantastic] * [http://world.honda.com/news/2005/c051219.html Honda to Mass Produce Next-Generation Thin Film Solar Cell] * [http://www1.eere.energy.gov/solar/solar_glossary.html Glossary]

[[Category:Infrared solar cells]] [[Category:Photovoltaics]]