Workfunction tuning of zinc oxide films by argon sputtering and oxygen plasma: an experimental and computational study

Kuo, Fang-Ling; Li, Yun; Solomon, Marvin; Du, Jincheng; Shepherd, Nigel D.

doi:10.1088/0022-3727/45/6/065301

Cited by 63 publications

(51 citation statements)

References 23 publications

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“…The role of the dopant, Cr in this case, produces an injection of electrons in the surface region due to the oxidation of the C 3 H 8 , as a consequence of the different between the work functions of the dopant [28] (Cr: 3.95–4.21 eV) [29] and the ZnO (4.5 eV) [30]. …”

Section: Resultsmentioning

confidence: 99%

Chromium and Ruthenium-Doped Zinc Oxide Thin Films for Propane Sensing Applications

Gómez-Pozos

González-Vidal

Torres

et al. 2013

Sensors

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Chromium and ruthenium-doped zinc oxide (ZnO:Cr) and (ZnO:Ru) thin solid films were deposited on soda-lime glass substrates by the sol-gel dip-coating method. A 0.6 M solution of zinc acetate dihydrate dissolved in 2-methoxyethanol and monoethanolamine was used as basic solution. Chromium (III) acetylacetonate and Ruthenium (III) trichloride were used as doping sources. The Ru incorporation and its distribution profile into the films were proved by the SIMS technique. The morphology and structure of the films were studied by SEM microscopy and X-ray diffraction measurements, respectively. The SEM images show porous surfaces covered by small grains with different grain size, depending on the doping element, and the immersions number into the doping solutions. The sensing properties of ZnO:Cr and ZnO:Ru films in a propane (C3H8) atmosphere, as a function of the immersions number in the doping solution, have been studied in the present work. The highest sensitivity values were obtained for films doped from five immersions, 5.8 and 900, for ZnO:Cr and ZnO:Ru films, respectively. In order to evidence the catalytic effect of the chromium (Cr) and ruthenium (Ru), the sensing characteristics of undoped ZnO films are reported as well.

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Section: Resultsmentioning

confidence: 99%

Chromium and Ruthenium-Doped Zinc Oxide Thin Films for Propane Sensing Applications

Gómez-Pozos

González-Vidal

Torres

et al. 2013

Sensors

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“…[ 9 ] The fi rst challenge has been addressed largely by synthesizing conjugated molecular and polymeric donor materials with smaller optical band gaps. system has achieved high PCE values of 7.5% in conventional OPV cells employing PEDOT:PSS, [ 31 ] 8.4% in inverted cells employing ZnO as the ETL, [ 33 ] and 8.6% with fl uorophthalocyanine nanowire ZnO functionalization. Regarding the second challenge, there are many means by which light absorption can be increased despite short exciton diffusion lengths.…”

Section: Doi: 101002/aenm201301938mentioning

confidence: 99%

High‐Efficiency Inverted Polymer Photovoltaics via Spectrally Tuned Absorption Enhancement

Loser

Valle

Luck

et al. 2014

Advanced Energy Materials

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For example, by systematically varying the thickness of the photoactive region (a tedious process), optical cavity modes that serve to enhance absorption can be tuned in frequency. [ 16 ] Furthermore, as we show here, optical transfer matrix simulations can be used to expeditiously optimize photocurrent generation in the photoactive region by shaping its absorption spectrum. In this contribution, transfer matrix calculations are shown to effectively guide OPV performance enhancement by spectral tuning in inverted polymer photovoltaic architectures.Since both donor and acceptor materials in the active layer contact both electrodes in BHJ cells, interfacial layers (IFLs) are typically introduced to minimize leakage currents. [ 17 ] In conventional OPV device architectures, where holes are collected at the transparent indium tin oxide (ITO) anode and electrons at the refl ective metal cathode, the archetypical IFL deposited on the ITO is the hole transport layer poly(3,4-ethylenedioxyle nethiophene):poly(styrenesulphonic acid) (PEDOT:PSS). However, this layer limits device lifetime since it is corrosive, [ 18 ] hygroscopic, [ 19 ] and thermally unstable, [ 20 ] motivating alternative IFL materials strategies. Thus, an inverted device architecture (Figure 1 ), where ITO collects electrons and a high work function metal electrode collects holes, has proven very effective in enhancing both OPV performance and durability. [ 21,22 ] In the present work, an electron transport layer (ETL) coating is deposited on the ITO cathode. Solution deposited zinc oxide (ZnO) is a particularly effective ETL in inverted OPVs due to its large bandgap, [ 23 ] high electron mobility, [ 24 ] solar transparency, [ 25 ] and well-positioned conduction band energy for use with electron acceptors, such as fullerene derivatives. [ 26 ] While recent literature has demonstrated higher PCEs using a polymeric ETL in the inverted OPV architecture, [ 27 ] sol-gel ZnO is inexpensive, environmentally friendly, [ 28 ] and a common ETL in inverted OPVs, motivating this study on its impact in optical cavity strategies. [ 29 ] In addition to its favorable ETL properties, ZnO has also been used as an optical spacer [ 30 ] when adjacent to the refl ective metal electrode, improving the distribution of optical intensity in conventional OPVs. In contrast, this work describes the very signifi cant consequences for the optical intensity distribution of placing a ZnO layer adjacent to the transparent electrode in inverted architecture OPVs.The inverted device architecture in this work utilizes a ZnO ETL and a BHJ active layer composed of the donor poly [[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl] [3-fl uoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]thiophenediyl]] (PTB7) and the acceptor [6,6]-phenyl C 71 butyric acid methyl-ester (PC 71 BM; Figure 1 ). The PTB7:PC 71 BM active layer has been previously shown to yield large internal quantum effi ciencies and exhibit absorption across much of the visible spectrum. [ 31,32 ] Furthermore, this a...

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“…The increase in carrier concentration in the accumulation layer was correlated (i) to a variation of the band bending that induces quasi-bidimensional confined trapped states 29,[33][34][35][36]42 and (ii) to a decrease in work function. These adsorbate-dependent 43 evolutions of the band levels were characterized by optical measurements 5 , macroscopic 6,44 or local Kelvin probes 45 , ultraviolet 43,46 , laboratory X-ray 40,41,[47][48][49] or synchrotron [34][35][36]41,42 photoemission. Atomic H adsorption systematically diminishes the work function, bends bands downward to create an accumulation layer 6,[33][34][35][36]42 by creating H-related levels that donate electrons to the conduction band.…”

Section: Introductionmentioning

confidence: 99%

Band alignment at Ag/ZnO(0001) interfaces: A combined soft and hard x-ray photoemission study

et al. 2018

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Band alignment at the interface between evaporated silver films and Zn-or O-terminated polar orientations of ZnO is explored by combining soft and hard X-ray photoemissions on native and hydrogenated surfaces. Ultraviolet Photoemission Spectroscopy (UPS) is used to track variations of work function, band bending, ionization energy and Schottky barrier during silver deposition.The absolute values of band bending and the bulk position of the Fermi level are determined on continuous silver films by HArd X-ray PhotoEmission Spectroscopy (HAXPES) through a dedicated modeling of core levels. Hydrogenation leads to the formation of ∼ 0.3 monolayer of donor-like hydroxyl groups on both ZnO-O and ZnO-Zn surfaces and to the release of metallic zinc on ZnO-Zn. However no transition to an accumulation layer is observed. On bare surfaces, silver adsorption is cationic on ZnO(0001)-O (anionic on ZnO(0001)-Zn) at the earliest stages of growth as expected from polarity healing before adsorbing as a neutral species. UPS and HAXPES data appear quite consistent. The two surfaces undergo rather similar band bendings for all types of preparation. The downward band bending of V bb,ZnO−O = −0.4 eV and V bb,ZnO−Zn = −0.6 eV found for the bare surfaces are reinforced for upon hydrogenation (V bb,ZnO−O+H = −1.1 eV, V bb,ZnO−Zn+H = −1.2 eV). At the interface with Ag, a unique value of band bending of -0.75 eV is observed. While exposure to atomic hydrogen modulates strongly the energetic positions of the surface levels, a similar Schottky barrier of 0.5-0.7 eV is found for thick silver films on the two surfaces.

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Workfunction tuning of zinc oxide films by argon sputtering and oxygen plasma: an experimental and computational study

Cited by 63 publications

References 23 publications

Chromium and Ruthenium-Doped Zinc Oxide Thin Films for Propane Sensing Applications

Chromium and Ruthenium-Doped Zinc Oxide Thin Films for Propane Sensing Applications

High‐Efficiency Inverted Polymer Photovoltaics via Spectrally Tuned Absorption Enhancement

Band alignment at Ag/ZnO(0001) interfaces: A combined soft and hard x-ray photoemission study

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