First-Principles Study on Water and Oxygen Adsorption on Surfaces of Indium Oxide and Indium Tin Oxide Nanoparticles

Zhou, Chenggang; Li, Jiaye; Chen, Su; Wu, Jingjie; Heier, Kevin R.; Cheng, Hansong

doi:10.1021/jp801229g

Cited by 37 publications

(46 citation statements)

References 25 publications

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“…A dimerized surface would be in agreement with other DFT calculations, which predict that surface oxygen atoms undergo a dimerization. 3,24 For the sputtered/annealed surface, we can safely rule out a (partial) peroxide termination for the following reasons: (i) The preparation included annealing to 800 K in an oxygen background pressure of less than 10 −12 mbar. This corresponds to an oxygen chemical potential of approximately −2 eV, assuming equilibrium with the residual gas.…”

Section: A Surface Structurementioning

confidence: 99%

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Bulk and surface characterization of In2O3(001) single crystals

et al. 2012

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A comprehensive bulk and surface investigation of high-quality In 2 O 3 (001) single crystals is reported. The transparent-yellow, cube-shaped single crystals were grown using the flux method. Inductively coupled plasma mass spectrometry (ICP-MS) reveals small residues of Pb, Mg, and Pt in the crystals. Four-point-probe measurements show a resistivity of 2.0 ± 0.5 × 10 5 cm, which translates into a carrier concentration of ≈10 12 cm −3 . The results from x-ray diffraction (XRD) measurements revise the lattice constant to 10.1150(5)Å from the previously accepted value of 10.117Å. Scanning tunneling microscopy (STM) images of a reduced (sputtered/annealed) and oxidized (exposure to atomic oxygen at 300• C) surface show a step height of 5Å, which indicates a preference for one type of surface termination. The surfaces stay flat without any evidence for macroscopic faceting under any of these preparation conditions. A combination of low-energy ion scattering (LEIS) and atomically resolved STM indicates an indium-terminated surface with small islands of 2.5Å height under reducing conditions, with a surface structure corresponding to a strongly distorted indium lattice. Scanning tunneling spectroscopy (STS) reveals a pronounced surface state at the Fermi level (E F ). Photoelectron spectroscopy (PES) shows additional, deep-lying band gap states, which can be removed by exposure of the surface to atomic oxygen. Oxidation also results in a shoulder at the O 1s core level at a higher binding energy, possibly indicative of a surface peroxide species. A downward band bending of 0.4 eV is observed for the reduced surface, while the band bending of the oxidized surface is of the order of 0.1 eV or less.

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Section: A Surface Structurementioning

confidence: 99%

“…1,18,24,[36][37][38] The CB is dominated by the In 5s states. Gap states of pure In 2 O 3 have been reported previously.…”

Section: Surface Statesmentioning

confidence: 99%

Bulk and surface characterization of In2O3(001) single crystals

et al. 2012

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“…11,21 Meanwhile, the adsorption of oxygen on ITO surface is commonly observed during oxygen plasma or ultraviolet (UV)-ozone treatments, 22,23 and molecular oxygen and water in the ambient air are also suggested to generate adsorbed oxygen on ITO. 24 Significantly, these adsorbed oxygen species can not only increase the work function of ITO 23,25 but also create midgap charge trap states on the organic semiconductor deposited on top by removing electrons from the organic layer (i.e., oxidation), even resulting in an irreversible degradation of the organic semiconductor as Lo et al reported recently. 23 Under these circumstances, we anticipate a presence of adsorbed oxygen on ITO during the ambient air processing and oxidation of the PFN coming into contact, ultimately inducing the formation of midgap charge trap states in the PFN interfaced with ITO.…”

Section: ■ Introductionmentioning

confidence: 99%

Ambient Air Processing Causes Light Soaking Effects in Inverted Organic Solar Cells Employing Conjugated Polyelectrolyte Electron Transfer Layer

Nam

2014

J. Phys. Chem. C

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Inverted polymer:fullerene bulk heterojunction solar cells employing a conjugated polyelectrolyte electron transfer layer display light soaking effects as the oxygen adsorbed on indium tin oxide (ITO) during an ambient air device processing induces interface charge trap states in the conjugated polyelectrolyte layer and reduces its interface dipole. The light soaking populates the trap states with photoexcited electrons and reinstates the electric dipole, leading to a recovery of efficient charge extraction and normal illuminated current−voltage characteristics consequently. The identified effect of adsorbed oxygen not only enables a remedy of the light soaking issue of the inverted solar cells via hydrogen plasma treatment of ITO but also suggests the importance of properly handling adsorbed oxygen species on ITO for achieving high performance organic devices based on ITO substrates in general. ■ INTRODUCTIONWith the champion efficiency approaching over 12% 1,2 and continuing commercialization efforts in the field, the attention to the organic solar cell continues. The structure of organic solar cells has been largely based on an active organic layer sandwiched between a transparent metal oxide bottom anode (typically indium tin oxide (ITO) coated with a hole transfer layer) and a metal cathode on top. Reversing the order, the inverted organic solar cell uses the bottom ITO as a cathode after applying a certain electron transfer layer (ETL) before depositing the active organic layer. The inverted structure is more attractive for a large-scale manufacturing, 2,3 displays a good ambient stability, 3,4 and in the case of polymer:fullerene bulk heterojunction (BHJ) active layer utilizes the natural composition gradient of BHJ, where the concentration of fullerene electron acceptor tends to increase toward the bottom. 5 For the ETL, the material choice has been mostly metal oxides (e.g., TiO x and ZnO), 2,6−9 but recently organic and organic−inorganic hybrid composite materials were also used. 6,10,11 Particularly, 9.2% power conversion efficiency (PCE) has been demonstrated by applying a conjugated organic polyelectrolyte PFN (poly [(9,Ndimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)) as an ETL, in conjunction with a low band gap polymer donor PTB7 (poly [[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]-thieno[3,4-b]thiophenediyl]]). 11Most of inverted organic solar cells adopting metal oxide ETLs display so-called light soaking effects, 2,7−9 wherein the device PCE increases with increasing duration of solar illumination due to increasing open circuit voltage (V OC ) and fill factor (FF). This gradual, light-sensitive change in photovoltaic (PV) characteristics is driven by a disappearance of the S-shaped current−voltage curve near the open circuit point, whose potential origins have been correlated to trap filling in the metal oxide layer and subsequent increase in photoconductivity; 7 energy barrier between ITO and the metal oxide ETL; 8 che...

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“…8 Density functional theory studies on the electronic structure of Sn-doped In 2 O 3 have revealed a n-type electrical behavior. [9][10][11][12] The conduction band minimum (CBM) of indium oxide is mainly contributed by the highly delocalized In-5s band. The Sn-5s states are strongly hybridized with the neighboring O-2p states, which donate electrons to the conduction band minimum.…”

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confidence: 99%

Electronic Structures and Transport Properties of n-Type-Doped Indium Oxides

et al. 2015

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Electrical and optical properties of transparent conducting oxides (TCOs) are of essential importance for optoelectronics. Electronic structures are keys to the understanding of these properties. The geometrical and electronic structures of body-centered cubic In 2 O 3 n-typedoped by Group 14 and fifth-period main group elements (Sb, Te and I) are systematically investigated. The calculated electronic structures reveal a good hybridization between the O-2p states and the s-states of Si, Ge and Sn, resulting in superior electronic properties, such as a freeelectron-like band feature, a large band width (> 2 eV), a low effective mass (m*=0.2m 0 ) and a high electron group velocity (≥8.35×10 5 m/s). The charge localization on the dopants leads to inferior electronic properties of In 2 O 3 doped by other dopants. The calculated defect formation energy indicates that the formation of both neutral and +1 charge state Sn is spontaneous in indium oxide.

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First-Principles Study on Water and Oxygen Adsorption on Surfaces of Indium Oxide and Indium Tin Oxide Nanoparticles

Cited by 37 publications

References 25 publications

Bulk and surface characterization of In2O3(001) single crystals

Bulk and surface characterization of In2O3(001) single crystals

Ambient Air Processing Causes Light Soaking Effects in Inverted Organic Solar Cells Employing Conjugated Polyelectrolyte Electron Transfer Layer

Electronic Structures and Transport Properties of n-Type-Doped Indium Oxides

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