Structure, stability and work functions of the low index surfaces of pure indium oxide and Sn-doped indium oxide (ITO) from density functional theory

Walsh, Aron; Catlow, C. Richard A.

doi:10.1039/c0jm01816c

Cited by 195 publications

(185 citation statements)

References 76 publications

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“…A simple band alignment derived from a charge neutrality level (CNL, or branch point energy) approach 20 is displayed in Figure 2. This approximate model places the ionization potential of In 2 O 3 at 7.81 eV, which is in good agreement with recent calculated 21 and experimental measurements. 22 Figure 3.…”

supporting

confidence: 77%

Band gap engineering of In2O3 by alloying with Tl2O3

Scanlon

Regoutz

Egdell

et al. 2013

Applied Physics Letters

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Efficient modulation of the bandgap of In2O3 will open up a route to improved electronic properties. We demonstrate using ab initio calculations that Tl incorporation into In2O3 reduces the band gap and confirm that narrowing of the gap is observed by X-ray photoemission spectroscopy on ceramic surfaces. Incorporation of Tl does not break the symmetry of the allowed optical transitions, meaning that the doped thin films should retain optical transparency in the visible region, in combination with a lowering of the conduction band effective mass. We propose that Tl-doping may be an efficient way to increase the dopability and carrier mobility of In2O3.

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supporting

confidence: 77%

Band gap engineering of In2O3 by alloying with Tl2O3

Scanlon

Regoutz

Egdell

et al. 2013

Applied Physics Letters

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“…The ITO work function and ionization potential considerably depend on the specific crystallographic surface as has been calculated for low index surfaces 75 and measured for epitaxially grown In 2 O 3 . 76 We derive the ITO work function from the secondary electron onset in UPS spectra [see Fig.…”

Section: Photoemission Studiesmentioning

confidence: 99%

Influence of the indium tin oxide/organic interface on open-circuit voltage, recombination, and cell degradation in organic small-molecule solar cells

et al. 2011

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In this paper we investigate the performance and stability of small-molecule organic solar cells with respect to the indium tin oxide (ITO)/organic interface. Different zinc-phthalocyanine (ZnPc)/fullerene (C 60 ) cell architectures with and without ITO O 2 -plasma treatment are compared and tested with respect to their degradation behavior under illumination in inert atmosphere. Photoelectron spectroscopy (UPS and XPS) shows that the O 2 -plasma treatment increases the ITO work function from 4.3 eV up to 5.6 eV. We find that both the increased ITO work function as well as the introduction of an electron blocking layer between ITO and the mixed donor/acceptor layer increases the open-circuit voltage V oc by more than 200 mV. For both cases our continuum approach device simulation quantitatively relates the increase of V oc to a reduced contact recombination and thus a reduced dark current. For cells built on ozone treated ITO we find a fast cell degradation caused by the UV part of the AM 1.5 spectrum. We identify the degradation, which manifests itself in a decrease of V oc of up to 25%, as a partial reversion of the plasma induced ITO work function increase. Additionally, we demonstrate that the degradation can be reduced by structural changes in the cell architecture, leading to improved cell stability. We present a comprehensive study of the recombination at the ITO/organic interface and its influence on the open-circuit voltage and the cell stability.

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“…Theoretical studies, however, vary widely in their predictions on the donor properties of vacancies, with some recent DFT studies predicting that vacancies are deep donors [39,42], which would seemingly contradict the experimental findings. One explanation that has been advanced is that, due to a reduction of formation energy, and consistent with observed surface electron densities, vacancies may occur in significant concentrations on the surface, where their ionization energies could be reduced [64][65][66][67][68][69]. Such a reduction in ionization energy, however, has not been demonstrated to occur due to the difficulty in calculating the properties of charged defects on surfaces using standard supercell techniques.…”

Section: Introductionmentioning

confidence: 99%

Deep vs shallow nature of oxygen vacancies and consequentn-type carrier concentrations in transparent conducting oxides

Buckeridge

Catlow

Farrow

et al. 2018

Phys. Rev. Materials

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The source of n-type conductivity in undoped transparent conducting oxides has been a topic of debate for several decades. The point defect of most interest in this respect is the oxygen vacancy, but there are many conflicting reports on the shallow versus deep nature of its related electronic states. Here, using a hybrid quantum mechanical/molecular mechanical embedded cluster approach, we have computed formation and ionization energies of oxygen vacancies in three representative transparent conducting oxides: In 2 O 3 , SnO 2 , and ZnO. We find that, in all three systems, oxygen vacancies form well-localized, compact donors. We demonstrate, however, that such compactness does not preclude the possibility of these states being shallow in nature, by considering the energetic balance between the vacancy binding electrons that are in localized orbitals or in effective-mass-like diffuse orbitals. Our results show that, thermodynamically, oxygen vacancies in bulk In 2 O 3 introduce states above the conduction band minimum that contribute significantly to the observed conductivity properties of undoped samples. For ZnO and SnO 2 , the states are deep, and our calculated ionization energies agree well with thermochemical and optical experiments. Our computed equilibrium defect and carrier concentrations, however, demonstrate that these deep states may nevertheless lead to significant intrinsic n-type conductivity under reducing conditions at elevated temperatures. Our study indicates the importance of oxygen vacancies in relation to intrinsic carrier concentrations not only in In 2 O 3 , but also in SnO 2 and ZnO.

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Structure, stability and work functions of the low index surfaces of pure indium oxide and Sn-doped indium oxide (ITO) from density functional theory

Cited by 195 publications

References 76 publications

Band gap engineering of In2O3 by alloying with Tl2O3

Band gap engineering of In2O3 by alloying with Tl2O3

Influence of the indium tin oxide/organic interface on open-circuit voltage, recombination, and cell degradation in organic small-molecule solar cells

Deep vs shallow nature of oxygen vacancies and consequentn-type carrier concentrations in transparent conducting oxides

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