Editing Organic electronics (section)

==Organic electronic devices==
{{Main|Organic solar cell|Photovoltaics}}
[[File:Flexible display.jpg|thumb|Organics-based [[flexible display]]]]
[[File:Organic photovoltaic material.pdf|thumb|Five structures of organic photovoltaic materials]]
[[Organic solar cell]]s could cut the cost of solar power compared with conventional solar-cell manufacturing.<ref>{{cite magazine |url=http://www.technologyreview.com/energy/21574/page1/ |title=Mass Production of Plastic Solar Cells |magazine=Technology Review |author=Bullis, Kevin |date=17 October 2008}}</ref> Silicon [[thin-film solar cell]]s on flexible substrates allow a significant cost reduction of large-area photovoltaics for several reasons:<ref name="ipe.uni-stuttgart.de">Koch, Christian (2002) [http://www.ipe.uni-stuttgart.de/index.php?lang=eng&pulldownID=12&ebene2ID=18&ID=3394 Niedertemperaturabscheidung von Dünnschicht-Silicium für Solarzellen auf Kunststofffolien], Doctoral Thesis, ipe.uni-stuttgart.de</ref>

# The so-called '[[roll-to-roll]]'-deposition on flexible sheets is much easier to realize in terms of technological effort than deposition on fragile and heavy [[glass sheet]]s.
# Transport and installation of lightweight flexible solar cells also saves cost as compared to cells on glass.

Inexpensive polymeric substrates like [[polyethylene terephthalate]] (PET) or [[polycarbonate]] (PC) have the potential for further cost reduction in photovoltaics. [[Protocrystalline|Protomorphous]] solar cells prove to be a promising concept for efficient and low-cost photovoltaics on cheap and flexible substrates for large-area production as well as small and mobile applications.<ref name="ipe.uni-stuttgart.de"/>

One advantage of [[printed electronics]] is that different electrical and electronic components can be printed on top of each other, saving space and increasing reliability and sometimes they are all transparent. One ink must not damage another, and low temperature annealing is vital if low-cost flexible materials such as paper and [[plastic film]] are to be used. There is much sophisticated engineering and chemistry involved here, with iTi, Pixdro, Asahi Kasei, Merck & Co.|Merck, BASF, HC Starck, Sunew, Hitachi Chemical, and Frontier Carbon Corporation among the leaders.<ref>{{Cite web |author=Raghu Das, IDTechEx |url=http://www.electronicsweekly.com/Articles/2008/09/25/44587/printed-electronics-is-it-a-niche.htm |title=Printed electronics, is it a niche? – 25 September 2008 |work=Electronics Weekly |date=25 September 2008 |access-date=14 February 2010}}</ref>
[[Electronic device]]s based on [[organic compound]]s are now widely used, with many new products under development. [[Sony]] reported the first full-color, video-rate, flexible, plastic display made purely of organic [[Chemical substance|materials]];<ref>[http://www.sony.co.jp/SonyInfo/News/Press/200705/07-053/index.html プラスチックフィルム上の有機TFT駆動有機ELディスプレイで世界初のフルカラー表示を実現]. sony.co.jp (in Japanese)</ref><ref>[http://pinktentacle.com/2007/05/flexible-full-color-organic-el-display/ Flexible, full-color OLED display]. pinktentacle.com (24 June 2007).</ref> [[television]] screen based on OLED materials; [[biodegradable]] electronics based on organic compound and low-cost organic [[solar cell]] are also available.

===Fabrication methods===
Small molecule semiconductors are often [[insoluble]], necessitating [[deposition (chemistry)|deposition]] via vacuum [[sublimation (phase transition)|sublimation]]. Devices based on [[conductive polymer]]s can be prepared by solution processing methods. Both solution processing and vacuum based methods produce amorphous and [[polycrystalline]] films with variable degree of disorder. "Wet" [[coating]] techniques require polymers to be dissolved in a volatile [[solvent]], filtered and deposited onto a [[substrate (materials science)|substrate]]. Common examples of solvent-based coating techniques include drop casting, [[spin-coating]], doctor-blading, [[inkjet printing]] and [[screen printing]]. Spin-coating is a widely used technique for small area [[thin film]] production. It may result in a high degree of material loss. The doctor-blade technique results in a minimal material loss and was primarily developed for large area thin film production. Vacuum based thermal deposition of small molecules requires [[evaporation]] of molecules from a hot source. The molecules are then transported through vacuum onto a substrate. The process of condensing these molecules on the substrate surface results in thin film formation. Wet coating techniques can in some cases be applied to small molecules depending on their solubility.

===Organic solar cells===
[[File:BilayerElectrode.pdf|thumb|Bilayer organic photovoltaic cell]]
Organic semiconductor diodes convert light into electricity. Figure to the right shows five commonly used organic photovoltaic materials. Electrons in these organic molecules can be delocalized in a delocalized π [[Molecular orbital|orbital]] with a corresponding π* antibonding [[Molecular orbital|orbital]]. The difference in energy between the π orbital, or highest occupied molecular orbital ([[HOMO]]), and π* orbital, or lowest unoccupied molecular orbital ([[LUMO]]) is called the [[band gap]] of organic photovoltaic materials. Typically, the [[band gap]] lies in the range of 1-4eV.<ref name="Nelson"/><ref name="HallsFriend"/><ref name="Hoppe"/>

The difference in the [[band gap]] of organic [[photovoltaic]] materials leads to different chemical structures and forms of organic [[solar cell]]s. Different forms of solar cells includes single-layer organic [[photovoltaic]] cells, bilayer organic [[photovoltaic]] cells and heterojunction [[photovoltaic]] cells. However, all three of these types of solar cells share the approach of sandwiching the organic electronic layer between two metallic conductors, typically [[indium tin oxide]].<ref name="McGehee"/>
[[File:Tft.png|thumb|Illustration of thin film transistor device]]

===Organic field-effect transistors===
An organic field-effect transistor is a three terminal device (source, drain and gate). The charge carriers move between source and drain, and the gate serves to control the path's conductivity. There are mainly two types of organic field-effect transistor, based on the semiconducting layer's charge transport, namely p-type (such as dinaphtho[2,3-''b'':2′,3′-''f'']thieno[3,2-''b'']thiophene, DNTT),<ref>{{Cite journal |last1=Sugiyama |first1=Masahiro |last2=Jancke |first2=Sophie |last3=Uemura |first3=Takafumi |last4=Kondo |first4=Masaya |last5=Inoue |first5=Yumi |last6=Namba |first6=Naoko |last7=Araki |first7=Teppei |last8=Fukushima |first8=Takanori |last9=Sekitani |first9=Tsuyoshi |date=September 2021 |title=Mobility enhancement of DNTT and BTBT derivative organic thin-film transistors by triptycene molecule modification |journal=Organic Electronics |language=en |volume=96 |pages=106219 |doi=10.1016/j.orgel.2021.106219|doi-access=free }}</ref> and n-type (such phenyl C61 butyric acid methyl ester, PCBM).<ref>{{Cite journal |last1=Anthony |first1=John E. |last2=Facchetti |first2=Antonio |last3=Heeney |first3=Martin |last4=Marder |first4=Seth R. |last5=Zhan |first5=Xiaowei |date=2010-09-08 |title=n-Type Organic Semiconductors in Organic Electronics |url=https://onlinelibrary.wiley.com/doi/10.1002/adma.200903628 |journal=Advanced Materials |language=en |volume=22 |issue=34 |pages=3876–3892 |doi=10.1002/adma.200903628|pmid=20715063 |bibcode=2010AdM....22.3876A |s2cid=205235378 }}</ref> Certain organic semiconductors can also present both p-type and n-type (i.e., ambipolar) characteristics.<ref>{{Cite journal |last1=Zhao |first1=Yan |last2=Guo |first2=Yunlong |last3=Liu |first3=Yunqi |date=2013-10-11 |title=25th Anniversary Article: Recent Advances in n-Type and Ambipolar Organic Field-Effect Transistors |url=https://onlinelibrary.wiley.com/doi/10.1002/adma.201302315 |journal=Advanced Materials |language=en |volume=25 |issue=38 |pages=5372–5391 |doi=10.1002/adma.201302315|pmid=24038388 |bibcode=2013AdM....25.5372Z |s2cid=6042903 }}</ref>

Such technology allows for the fabrication of large-area, flexible, low-cost electronics.<ref>{{Cite journal |last1=Di |first1=Chong-an |last2=Zhang |first2=Fengjiao |last3=Zhu |first3=Daoben |date=2013-01-18 |title=Multi-Functional Integration of Organic Field-Effect Transistors (OFETs): Advances and Perspectives |url=https://onlinelibrary.wiley.com/doi/10.1002/adma.201201502 |journal=Advanced Materials |language=en |volume=25 |issue=3 |pages=313–330 |doi=10.1002/adma.201201502|pmid=22865814 |bibcode=2013AdM....25..313D |s2cid=26645918 }}</ref> One of the main advantages is that being mainly a low temperature process compared to CMOS, different type of materials can be utilized. This makes them in turn great candidates for sensing.<ref>{{Cite journal |last1=Dudhe |first1=Ravishankar S. |last2=Sinha |first2=Jasmine |last3=Kumar |first3=Anil |last4=Rao |first4=V. Ramgopal |date=2010-06-30 |title=Polymer composite-based OFET sensor with improved sensitivity towards nitro based explosive vapors |url=https://www.sciencedirect.com/science/article/pii/S0925400510003503 |journal=Sensors and Actuators B: Chemical |language=en |volume=148 |issue=1 |pages=158–165 |doi=10.1016/j.snb.2010.04.022 |bibcode=2010SeAcB.148..158D |issn=0925-4005}}</ref>