Nobel Lecture: Semiconducting and metallic polymers: The fourth generation of polymeric materials

Heeger, Alan J.

doi:10.1103/revmodphys.73.681

Cited by 750 publications

(484 citation statements)

References 87 publications

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“…Conducting polymers [197][198][199] can exhibit rather high optical transparency [200]. Meanwhile, thin-films of carbon nanotubes have been created which are both conducting and highly transparent [201,202].…”

Section: Discussionmentioning

confidence: 99%

Conductivity in transparent oxide semiconductors

King

Veal

2011

J. Phys.: Condens. Matter

222

180

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Abstract. Despite an extensive research effort for over 60 years, an understanding of the origins of conductivity in wide band-gap transparent conducting oxide (TCO) semiconductors remains elusive. While TCOs have already found widespread use in device applications requiring a transparent contact, there are currently enormous efforts to (i) increase the conductivity of existing materials, (ii) identify suitable alternatives, and (iii) attempt to gain semiconductor-engineering levels of control over their carrier density, essential for the incorporation of TCOs into a new generation of multifunctional transparent electronic devices. These efforts, however, are dependent on a microscopic identification of the defects and impurities leading to the high unintentional carrier densities present in these materials. Here, we review recent developments towards such an understanding. While oxygen vacancies are commonly assumed to be the source of the conductivity, there is increasing evidence that this is not a sufficient mechanism to explain the total measured carrier concentrations. In fact, many studies suggest that oxygen vacancies are deep, rather than shallow, donors, and their abundance in as-grown material is also debated. We discuss other potential contributions to the conductivity in TCOs, including other native defects, their complexes, and in particular hydrogen impurities. Convincing theoretical and experimental evidence is presented for the donor nature of hydrogen across a range of TCO materials, and while its stability and the presence of interstitial and substitutional species are still somewhat open questions, it is one of the leading contenders for unintentional conductivity in TCOs. We also review recent work indicating that the surfaces of TCOs can support very high carrier densities, opposite to the case of conventional semiconductors. In thin-film materials/devices and, in particular, nanostructures, the surface can have a large impact on the total conductivity in TCOs. We discuss models that attempt to explain both the bulk and surface conductivity based on features of the bulk band structure common across the TCOs, and compare these materials to other semiconductors. Finally, we briefly consider transparency in these materials, and its interplay with conductivity. Understanding this interplay, as well as the microscopic contenders for the conductivity of these materials, will prove essential to the future design and control of TCO semiconductors, and their implementation into novel multifunctional devices.

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Section: Discussionmentioning

confidence: 99%

Conductivity in transparent oxide semiconductors

King

Veal

2011

J. Phys.: Condens. Matter

222

180

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“…[ 12,13 ] Interestingly, the thermal conductivity of bulk polymers as well as conjugated macromolecules can be tuned by controlling molecular orientation. [14][15][16] In order to increase the modest electrical conductivity of polymers, a number of strategies have been proposed, including careful doping, [ 4,11,[17][18][19][20][21] making composites of polymers with conductive fi llers such as CNTs, [22][23][24] or fabricating multilayer composite A broad range of organic electronic applications rely on the availability of both p-and n-type organic semiconductors, and the possibility to deposit them as sequential layers or to form spatial patterns. Examples include transport layers in diodes (OLEDs, photovoltaics, etc.…”

Section: Doi: 101002/adma201505521mentioning

confidence: 99%

Photoinduced p‐ to n‐type Switching in Thermoelectric Polymer‐Carbon Nanotube Composites

et al. 2016

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“…35 The prototypical example of a one-dimensional (1D) conducting polymer is trans-polyacetylene (trans-PA). The idealized structure of trans-PA can be described as a chain of equally spaced CH groups.…”

Section: Amorphous Nitrogenmentioning

confidence: 99%

Electronic and structural properties of dense liquid and amorphous nitrogen

Boates

Bonev

2011

Phys. Rev. B

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We present first-principles calculations of the structural and electronic properties of liquid nitrogen in the pressure-temperature range of 0-200 GPa and 2000-6000 K. Upon polymerization, the liquid becomes metallic, similar to what has been reported for the higher-temperature atomic fluid. An explanation of the electronic properties of the transformed liquids and the differences with the electronic properties of insulating solid cubic-gauche nitrogen is given based on the structure and bonding character of these phases. The mechanism responsible for charge transport in polymeric nitrogen systems is examined in order to understand the semi-conducting nature of low-temperature amorphous nitrogen.

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Nobel Lecture: Semiconducting and metallic polymers: The fourth generation of polymeric materials

Cited by 750 publications

References 87 publications

Conductivity in transparent oxide semiconductors

Conductivity in transparent oxide semiconductors

Photoinduced p‐ to n‐type Switching in Thermoelectric Polymer‐Carbon Nanotube Composites

Electronic and structural properties of dense liquid and amorphous nitrogen

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