Electronic Coupling - Revision history

Cmditradmin: /* Polydiacetylene */

2010-08-10T23:28:07Z

Polydiacetylene

← Older revision		Revision as of 16:28, 10 August 2010
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	Polydiacetylene crystals have a pattern of double, single, triple, single bonds in their chain. They form perfect crystals when they have bulky side groups like pTS or pFBS. The problem is that because of the bulky side groups chains are pretty far from one another .If you could build a device with a single chain from one electrode to another that would be ideal; the carrier would zip through the chain from one side to another. If the carrier sees a defect it gets stuck because it is difficult to hop to an adjacent chain due to the large distance. Michel Schott has demonstrated macroscopic coherence of a single exciton along an isolated polydiacetylene chain with coherence length over tens of micrometers. These are some of the most perfect π conjugated chains that have been characterized. With a perfect chain the exciton can delocalize across the whole chain forming an exciton band. Polydiacetylene can have and a t along chains of about 2.0 eV.		Polydiacetylene crystals have a pattern of double, single, triple, single bonds in their chain. They form perfect crystals when they have bulky side groups like pTS or pFBS. The problem is that because of the bulky side groups chains are pretty far from one another .If you could build a device with a single chain from one electrode to another that would be ideal; the carrier would zip through the chain from one side to another. If the carrier sees a defect it gets stuck because it is difficult to hop to an adjacent chain due to the large distance. Michel Schott has demonstrated macroscopic coherence of a single exciton along an isolated polydiacetylene chain with coherence length over tens of micrometers. These are some of the most perfect π conjugated chains that have been characterized. With a perfect chain the exciton can delocalize across the whole chain forming an exciton band. Polydiacetylene can have and a t along chains of about 2.0 eV.

	See Schott 2006 <ref>M. Schott et al., Nature Physics 2, 32 (2006)</ref>		See Schott 2006 <ref>M. Schott et al., "Macroscopic coherence of a single exciton state in an organic quantum wire" Nature Physics 2, 32 (2006) {{Doi\|10.1038/nphys196}}</ref>

	=== Carbon nanotubes ===		=== Carbon nanotubes ===

Cmditradmin: /* Carbon nanotubes */

2010-08-10T23:23:42Z

Carbon nanotubes

← Older revision		Revision as of 16:23, 10 August 2010
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	Ballistic transport over 500 nm long nanotubes has bee measured:~ 80,000-100,000 cm<sup>2</sup>/Vs		Ballistic transport over 500 nm long nanotubes has bee measured:~ 80,000-100,000 cm<sup>2</sup>/Vs

	See Durkop 2004 <ref>T. Durkop, S.A. Getty, E. Cobas, and M.S. Fuhrer, NanoLett. 4, 35 (2004)</ref>		See Durkop 2004 <ref>T. Durkop, S.A. Getty, E. Cobas, and M.S. Fuhrer,"Extraordinary Mobility in Semiconducting Carbon Nanotubes" NanoLett. 4, 35 (2004) {{Doi\|10.1021/nl034841q}}</ref>

	Bulk graphite		Bulk graphite

Cmditradmin: /* Ladder polyparaphylenes */

2010-08-10T23:15:49Z

Ladder polyparaphylenes

← Older revision		Revision as of 16:15, 10 August 2010
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	See Prins 2006 <ref>P. Prins, L. Siebbeles, et al., Physical Review Letters 96, 146601 (2006)</ref>		See Prins 2006 <ref>P. Prins, L. Siebbeles, et al.,"High Intrachain Hole Mobility on Molecular Wires of Ladder-Type Poly(p-Phenylenes)" Physical Review Letters 96, 146601 (2006){{Doi\|10.1103/PhysRevLett.96.146601}}</ref>

	===Polythiophene film===		===Polythiophene film===

Cmditradmin: /* Carbon nanotubes */

2009-12-01T23:27:03Z

Carbon nanotubes

← Older revision		Revision as of 16:27, 1 December 2009
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	[[Image:Kohlenstoffnanoroehre_Animation.gif\|thumb\|300px\|A carbon nanotube]]		[[Image:Kohlenstoffnanoroehre_Animation.gif\|thumb\|300px\|A carbon nanotube]]

	~~see [http://www.chemspider.com/ImageView.aspx?id=21782456&mode=3d Jmol version of carbon nanotube]~~

	Carbon nanotubes produce a fairly rigid system because each carbon is bound and little vibration is possible.		Carbon nanotubes produce a fairly rigid system because each carbon is bound and little vibration is possible.
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	Thus, localization energy quickly competes with delocalization energy and the band regime is less easy to sustain upon increasing temperature.		Thus, localization energy quickly competes with delocalization energy and the band regime is less easy to sustain upon increasing temperature.

			see [http://www.chemspider.com/ImageView.aspx?id=21782456&mode=3d Jmol version of carbon nanotube]

	== References ==		== References ==

Cmditradmin: /* Carbon nanotubes */

2009-12-01T23:23:36Z

Carbon nanotubes

← Older revision		Revision as of 16:23, 1 December 2009
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	=== Carbon nanotubes ===		=== Carbon nanotubes ===
	[[Image:Kohlenstoffnanoroehre_Animation.gif\|thumb\|300px\|A carbon nanotube]]		[[Image:Kohlenstoffnanoroehre_Animation.gif\|thumb\|300px\|A carbon nanotube]]

			see [http://www.chemspider.com/ImageView.aspx?id=21782456&mode=3d Jmol version of carbon nanotube]

	Carbon nanotubes produce a fairly rigid system because each carbon is bound and little vibration is possible.		Carbon nanotubes produce a fairly rigid system because each carbon is bound and little vibration is possible.

Cmditradmin: /* Polythiophene film */

2009-12-01T19:18:23Z

Polythiophene film

← Older revision		Revision as of 12:18, 1 December 2009
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	Polythiophene (PT) is one of the most common polymers used in organic photovoltaics due to its desirable band gap, absorption, compatiblity with C-60, and high performance.		Polythiophene (PT) is one of the most common polymers used in organic photovoltaics due to its desirable band gap, absorption, compatiblity with C-60, and high performance.

	Because of the macrostructure of polymers, conduction is anisotropic. Polythiophene when applied as a film tends to stand on edge so it forms sheets with π-π stacking and is therefore anisotropic. Conduction in polythiphene is greatest in the p-p stacking direction, followed by a slower conduction in the direction aligned with polymer chain, and finally the lowest charge mobility is between the chains where there is a large distance to hop. Therefore to maximize charge mobility we must maximize π-π stacking. People are trying to make longer chains to increase stacking, however increased stacking means the solvent can't penetrate and these are less soluble and have reduced solution processibility. The addition of alkyl chains increases solubility however this decreases the π-π stacking. The challenge is to strike the right balance between performance and ease of solution processing.		Because of the macrostructure of polymers, conduction is anisotropic. Polythiophene when applied as a film tends to stand on edge so it forms sheets with π-π stacking and is therefore anisotropic. Conduction in polythiphene is greatest in the π-π stacking direction, followed by a slower conduction in the direction aligned with polymer chain, and finally the lowest charge mobility is between the chains where there is a large distance to hop. Therefore to maximize charge mobility we must maximize π-π stacking. People are trying to make longer chains to increase stacking, however increased stacking means the solvent can't penetrate and these are less soluble and have reduced solution processibility. The addition of alkyl chains increases solubility however this decreases the π-π stacking. The challenge is to strike the right balance between performance and ease of solution processing.

	=== Polydiacetylene ===		=== Polydiacetylene ===

Cmditradmin at 19:17, 1 December 2009

2009-12-01T19:17:16Z

← Older revision		Revision as of 12:17, 1 December 2009
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	=== Transpolyacetylene ===		=== Transpolyacetylene ===
	[[Image:Transpolyacetylene_unit.png\|thumb\|300px\|The repeating unit of transpolyacetylene is shown]]		[[Image:Transpolyacetylene_unit.png\|thumb\|300px\|The repeating unit of transpolyacetylene is shown]]
	In perfectly coplanar extended transpolyacetylene chain the electron coupling between adjacent units t (the transfer integral) is on the order of 2.5 – 3eV. Across the entire bandwidth ~~you have about~~ 20 eV.		In perfectly coplanar extended transpolyacetylene chain the electron coupling between adjacent units t (the transfer integral) is on the order of 2.5 – 3eV. Across the entire bandwidth there is 20 eV.

	In actual samples there is conductivity (σ) of 10<sup>5</sup> S/cm. Conductivity is charge times mobility times charge carrier density. With reasonable assumptions ~~you~~ can calculate a carrier density of 5 x 10<sup>21</sup> cm<sup>-3</sup> which gives a mobility of μ ~ 100-200 cm<sup>2</sup>/Vs. The best organic semiconductors with three dimensional lattice and low coupling through vibrations have mobilities of 1000s of cm<sup>2</sup>/Vs.		In actual samples there is conductivity (σ) of 10<sup>5</sup> S/cm. Conductivity is charge times mobility times charge carrier density. With reasonable assumptions one can calculate a carrier density of 5 x 10<sup>21</sup> cm<sup>-3</sup> which gives a mobility of μ ~ 100-200 cm<sup>2</sup>/Vs. The best organic semiconductors with three dimensional lattice and low coupling through vibrations have mobilities of 1000s of cm<sup>2</sup>/Vs.

	<br clear='all'>		<br clear='all'>

Cmditradmin: /* Polythiophene film */

2009-11-24T00:22:10Z

Polythiophene film

← Older revision		Revision as of 17:22, 23 November 2009
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	===Polythiophene film===		===Polythiophene film===
	[[Image:PT_film.png\|thumb\|300px\|Stacking in a polythiophene film]]		[[Image:PT_film.png\|thumb\|300px\|Stacking in a polythiophene film]]
	Polythiophene (~~P3HT~~) is one of the most common polymers used in organic photovoltaics due to its desirable band gap, absorption, compatiblity with C-60, and high performance.		Polythiophene (PT) is one of the most common polymers used in organic photovoltaics due to its desirable band gap, absorption, compatiblity with C-60, and high performance.

	Because of the macrostructure of polymers, conduction is anisotropic. Polythiophene when applied as a film tends to stand on edge so it forms sheets with π-π stacking and is therefore anisotropic. Conduction in polythiphene is greatest in the p-p stacking direction, followed by a slower conduction in the direction aligned with polymer chain, and finally the lowest charge mobility is between the chains where there is a large distance to hop. Therefore to maximize charge mobility we must maximize π-π stacking. People are trying to make longer chains to increase stacking, however increased stacking means the solvent can't penetrate and these are less soluble and have reduced solution processibility. The addition of alkyl chains increases solubility however this decreases the π-π stacking. The challenge is to strike the right balance between performance and ease of solution processing.		Because of the macrostructure of polymers, conduction is anisotropic. Polythiophene when applied as a film tends to stand on edge so it forms sheets with π-π stacking and is therefore anisotropic. Conduction in polythiphene is greatest in the p-p stacking direction, followed by a slower conduction in the direction aligned with polymer chain, and finally the lowest charge mobility is between the chains where there is a large distance to hop. Therefore to maximize charge mobility we must maximize π-π stacking. People are trying to make longer chains to increase stacking, however increased stacking means the solvent can't penetrate and these are less soluble and have reduced solution processibility. The addition of alkyl chains increases solubility however this decreases the π-π stacking. The challenge is to strike the right balance between performance and ease of solution processing.

Cmditradmin: /* Polythiophene film */

2009-11-24T00:21:05Z

Polythiophene film

← Older revision		Revision as of 17:21, 23 November 2009
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	===Polythiophene film===		===Polythiophene film===
	[[Image:PT_film.png\|thumb\|300px\|Stacking in a polythiophene film]]		[[Image:PT_film.png\|thumb\|300px\|Stacking in a polythiophene film]]
			Polythiophene (P3HT) is one of the most common polymers used in organic photovoltaics due to its desirable band gap, absorption, compatiblity with C-60, and high performance.

	Because of the macrostructure of polymers, conduction is anisotropic. Polythiophene when applied as a film tends to stand on edge so it forms sheets with π-π stacking and is therefore anisotropic. Conduction in polythiphene is greatest in the p-p stacking direction, followed by a slower conduction in the direction aligned with polymer chain, and finally the lowest charge mobility is between the chains where there is a large distance to hop. Therefore we must maximize π-π stacking. People are trying to make longer chains to increase stacking however these are less soluble and have reduced solution processibility. The addition of alkyl chains increases solubility however this decreases the π-π stacking. The challenge is to strike the right balance between performance and ease of solution processing.		Because of the macrostructure of polymers, conduction is anisotropic. Polythiophene when applied as a film tends to stand on edge so it forms sheets with π-π stacking and is therefore anisotropic. Conduction in polythiphene is greatest in the p-p stacking direction, followed by a slower conduction in the direction aligned with polymer chain, and finally the lowest charge mobility is between the chains where there is a large distance to hop. Therefore to maximize charge mobility we must maximize π-π stacking. People are trying to make longer chains to increase stacking, however increased stacking means the solvent can't penetrate and these are less soluble and have reduced solution processibility. The addition of alkyl chains increases solubility however this decreases the π-π stacking. The challenge is to strike the right balance between performance and ease of solution processing.

	=== Polydiacetylene ===		=== Polydiacetylene ===

Cmditradmin: /* Polythiophene film */

2009-11-24T00:13:51Z

Polythiophene film

← Older revision		Revision as of 17:13, 23 November 2009
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	[[Image:PT_film.png\|thumb\|300px\|Stacking in a polythiophene film]]		[[Image:PT_film.png\|thumb\|300px\|Stacking in a polythiophene film]]

	Because of the macrostructure of polymers, conduction is anisotropic. Polythiophene when applied as a film tends to stand on edge so it forms sheets with p-p stacking and is therefore anisotropic. Conduction in polythiphene is greatest in the p-p stacking direction, followed by a slower conduction in the direction aligned with polymer chain, and finally the lowest charge mobility is between the chains where there is a large distance to hop. Therefore we must maximize p-p stacking. People are trying to make longer chains to increase stacking however these are less soluble and ~~reducing~~ solution processibility. The addition of alkyl chains increases solubility however this decreases the pi-pi stacking. It challenge to ~~trade off~~ performance ~~with~~ ease of solution processing.		Because of the macrostructure of polymers, conduction is anisotropic. Polythiophene when applied as a film tends to stand on edge so it forms sheets with π-π stacking and is therefore anisotropic. Conduction in polythiphene is greatest in the p-p stacking direction, followed by a slower conduction in the direction aligned with polymer chain, and finally the lowest charge mobility is between the chains where there is a large distance to hop. Therefore we must maximize π-π stacking. People are trying to make longer chains to increase stacking however these are less soluble and have reduced solution processibility. The addition of alkyl chains increases solubility however this decreases the π-π stacking. The challenge is to strike the right balance between performance and ease of solution processing.

	=== Polydiacetylene ===		=== Polydiacetylene ===