Transparent conducting oxides for electrode applications in light emitting and absorbing devices

Liu, Huiyong; Avrutin, Vitaliy; Izyumskaya, N.; Özgür, Ü.; Morkoç̌, H.

doi:10.1016/j.spmi.2010.08.011

Cited by 564 publications

(301 citation statements)

References 252 publications

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“…Classic examples of n-type doped transparent conductors are Sn-doped In 2 O 3 (ITO), F-doped SnO 2 (FTO), doped zinc oxide (ZnO), and cadmium oxide (CdO). [4,[22][23][24][25] Conductive polymers such as poly (3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid (PEDOT:PSS) also partially offer both intrinsic properties. [26][27][28] A second strategy consists of dimensional engineering using conductive, but not necessarily transparent materials (e.g., metals or carbon-based materials [29] ) and their arrangement in such a way that the system conducts in one direction and is transparent in the other.…”

Section: Materials Systems For Transparent Electrodesmentioning

confidence: 99%

Transparent Electrodes for Efficient Optoelectronics

Morales‐Masis

Wolf

Woods‐Robinson

et al. 2017

Adv Elect Materials

354

288

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With the development of new generations of optoelectronic devices that combine high performance and novel functionalities (e.g., flexibility/bendability, adaptability, semi or full transparency), several classes of transparent electrodes have been developed in recent years. These range from optimized transparent conductive oxides (TCOs), which are historically the most commonly used transparent electrodes, to new electrodes made from nano‐ and 2D materials (e.g., metal nanowire networks and graphene), and to hybrid electrodes that integrate TCOs or dielectrics with nanowires, metal grids, or ultrathin metal films. Here, the most relevant transparent electrodes developed to date are introduced, their fundamental properties are described, and their materials are classified according to specific application requirements in high efficiency solar cells and flexible organic light‐emitting diodes (OLEDs). This information serves as a guideline for selecting and developing appropriate transparent electrodes according to intended application requirements and functionality.

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Section: Materials Systems For Transparent Electrodesmentioning

confidence: 99%

Transparent Electrodes for Efficient Optoelectronics

Morales‐Masis

Wolf

Woods‐Robinson

et al. 2017

Adv Elect Materials

354

288

View full text Add to dashboard Cite

show abstract

Section: Introductionmentioning

confidence: 99%

“…1 TCO films with high conductivity resulting from the high mobility rather than from high carrier concentration are desired in photovoltaics because of the unwanted free carrier absorption in the IR spectral range while retaining conductivity owing to relatively high mobility. 1 The reported mobility for GZO and AZO films grown by different techniques scatters from as low as $5 to as high as 70 cm 2 =VÁs for electron carrier concentrations exceeding 10 20 cm À3 . 1 It is generally accepted that the wide dispersion in the mobility is due to the differences in materials quality since the substrate temperature, film thickness, annealing conditions, and reactant compositions all affect the electrical properties.…”

Section: Introductionmentioning

confidence: 99%

Electron scattering mechanisms in GZO films grown on a-sapphire substrates by plasma-enhanced molecular beam epitaxy

Liu¹,

Avrutin²,

Izyumskaya³

et al. 2012

Journal of Applied Physics

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We report on the mechanisms governing electron transport using a comprehensive set of ZnO layers heavily doped with Ga (GZO) grown by plasma-enhanced molecular-beam epitaxy on a-plane sapphire substrates with varying oxygen-to-metal ratios and Ga fluxes. The analyses were conducted by temperature dependent Hall measurements which were supported by microstructural investigations as well. Highly degenerate GZO layers with n > 5 Â 10 20 cm À3 grown under metalrich conditions (reactive oxygen-to-metal ratio <1) show relatively larger grains ($20-25 nm by x-ray diffraction) with low-angle boundaries parallel to the polar c-direction. For highly conductive GZO layers, ionized-impurity scattering with almost no compensation is the dominant mechanism limiting the mobility in the temperature range from 15 to 330 K and the grain-boundary scattering governed by quantum-mechanical tunnelling is negligible. However, due to the polar nature of ZnO having high crystalline quality, polar optical phonon scattering cannot be neglected for temperatures above 150 K, because it further reduces mobility although its effect is still substantially weaker than the ionized impurity scattering even at room temperature (RT). Analysis of transport measurements and sample microstructures by x-ray diffraction and transmission electron microscopy led to a correlation between the grain sizes in these layers and mobility even for samples with a carrier concentration in the upper 10 20 cm À3 range. In contrast, electron transport in GZO layers grown under oxygen-rich conditions (reactive oxygen-to-metal ratio >1), which have inclined grain boundaries and relatively smaller grain sizes of 10-20 nm by x-ray diffraction, is mainly limited by compensation caused by acceptor-type point-defect complexes, presumably (Ga Zn -V Zn ), and scattering on grain boundaries. The GZO layers with n <10 20 cm À3 grown under metal-rich conditions with reduced Ga fluxes show a clear signature of grain-boundary scattering governed by the thermionic effect in the temperature-dependent mobility but with much higher RT mobility values compared to the samples grown under oxygen-rich conditions [34 vs. 7.5 cm 2 =VÁs]. Properties of GZO layers grown under different conditions clearly indicate that to achieve highly conductive GZO, metal-rich conditions instead of oxygen-rich conditions have to be used. V C 2012 American Institute of Physics. [http://dx

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“…[1][2][3][4][5] Low cost AZO is suitable for large-area applications such as displays and solar cells, while GZO is finding applications in solid-state optoelectronics due to higher performance. GZO has very low stress-strain constraints on doping compared to AZO and ITO, because the Ga-O bond length, 1.88 Å , is very close to the Zn-O bond length, 1.97 Å , 6 resulting in potentially higher mobility and carrier concentration.…”

Section: Introductionmentioning

confidence: 99%

Impurity distribution and microstructure of Ga-doped ZnO films grown by molecular beam epitaxy

Kvit

Yankovich

Avrutin

et al. 2012

Journal of Applied Physics

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We report microstructural characterization of heavily Ga-doped ZnO (GZO) thin films on GaN and sapphire by aberration-corrected scanning transmission electron microscopy. Growth under oxygen-rich and metal-rich growth conditions leads to changes in the GZO polarity and different extended defects. For GZO layers on sapphire, the primary extended defects are voids, inversion domain boundaries, and low-angle grain boundaries. Ga doping of ZnO grown under metal-rich conditions causes a switch from pure oxygen polarity to mixed oxygen and zinc polarity in small domains. Electron energy loss spectroscopy and energy dispersive spectroscopy spectrum imaging show that Ga is homogeneous, but other residual impurities tend to accumulate at the GZO surface and at extended defects. GZO grown on GaN on c-plane sapphire has Zn polarity and no voids. There are misfit dislocations at the interfaces between GZO and an undoped ZnO buffer layer and at the buffer/GaN interface. Low-angle grain boundaries are the only threading microstructural defects. The potential effects of different extended defects and impurity distributions on free carrier scattering are discussed. V C 2012 American Institute of Physics. [http://dx

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Transparent conducting oxides for electrode applications in light emitting and absorbing devices

Cited by 564 publications

References 252 publications

Transparent Electrodes for Efficient Optoelectronics

Transparent Electrodes for Efficient Optoelectronics

Electron scattering mechanisms in GZO films grown on a-sapphire substrates by plasma-enhanced molecular beam epitaxy

Impurity distribution and microstructure of Ga-doped ZnO films grown by molecular beam epitaxy

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