Electronic structure of Vanadium pentoxide: An efficient hole injector for organic electronic materials

Meyer, Jens; Zilberberg, Kirill; Riedl, Thomas; Kahn, Antoine

doi:10.1063/1.3611392

Cited by 243 publications

(198 citation statements)

References 35 publications

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“…Recently, a very high ionization potential of 9.5 eV was reported for V 2 O 5 along with a high work function of 7 eV and a Fermi level close to the conduction band minimum. 50 This seems to indicate that QSGW (10.9 eV) overestimates the ionization potential by about 1.5-2.0 eV which is somewhat larger than what is found for most semiconductors by Grüneis et al 57 . We note that the size quantization effects in a monolayer are expected to shift up the electron states and hence reduce the ionization potential compared to that near a surface of a bulk crystal.…”

Section: Monolayer Band Structure and Dielectric Constants In Qsgwmentioning

confidence: 45%

Quasiparticle self-consistentGWcalculations of the electronic band structure of bulk and monolayerV2O5

2015

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Quasiparticle self-consistent (QS) GW calculations are performed for bulk and monolayer V2O5. The orbital character of the bands and the bulk monolayer difference at the LDA level are discussed first. We find that the QSGW self-energy overestimates the gap by an unusually large amount. The main reason for this is identified to be the lattice polarization effect: the large LO-TO splittings in this polar material enhance the screening and reduce the screened Coulomb interaction affecting the gap. The effect is estimated to reduce the screened Coulomb interaction and hence the self-energy by a factor 0.38 (for bulk) and brings the calculated optical response functions in fairly good agreement with experiment. For monolayer V2O5, we find that the QSGW gap varies as 1/L with L the size of the spacing between the monolayers in a supercell. This results from the long-range nature of the self-energy Σ = iGW and the similar 1/L behavior of the dielectric screening.

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Section: Monolayer Band Structure and Dielectric Constants In Qsgwmentioning

confidence: 45%

Quasiparticle self-consistentGWcalculations of the electronic band structure of bulk and monolayerV2O5

2015

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“…The effect of the WML PFN on substrates of conducting (also highly doped semiconductors like p-type doped Si, p-type doped PEDOT:PSS and n-type doped V 2 O 5 , [ 26 ] prepared following the procedure reported in Ref. [ 27 ] , semiconducting (intrinsic), or insulating nature was measured as shown in Figure 3 and Table 1 .…”

Section: Work Function Reduction By Pfnmentioning

confidence: 99%

Origin of Work Function Modification by Ionic and Amine‐Based Interface Layers

Reenen

Kouijzer

Janssen

et al. 2014

Adv Materials Inter

130

138

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can evolve into a successful thin fi lm photovoltaic technology. To this end, further improvements in the sunlight-toelectricity conversion effi ciency are still needed. To do so, not only the optoelectronic, active layer should be considered, but also the connection between this layer and the electrodes. This connection is facilitated by so-called work function modifi cation layers (WMLs) that serve to align the transport levels in the organic semiconductor and the conductor by modifi cation of the work function. Materials that are often used are poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) for improving hole collection and injection in combination with an indium tin oxide (ITO) electrode and LiF for the electron contact in combination with an Al metal electrode. A new generation of WMLs fi rst introduced by Cao et al. is based on polyelectrolytes or tertiary aliphatic amines, such as poly [(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt -2,7-(9,9-dioctylfluorene)] (PFN) and the corresponding ethyl ammonium bromide. [ 1 ] Although these materials improve carrier injection or extraction in different organic diode devices, [1][2][3][4][5][6][7] the mechanism behind this improvement is not completely clear. This ambiguity hinders design, selection and optimization of new WMLs.Mechanisms that are generally considered to result in electric fi elds and concomitant work function shifts at metal-organic interfaces are doping, charge transfer, and dipole formation. [8][9][10] Regarding the work function modifi cation of amine side-groups, Lindell et al. [ 11 ] found by photoelectron spectroscopy and density functional calculations that the electron donor para-phenylenediamine chemisorbs onto atomically clean Ni in vacuum. [ 12 ] Due to partial electron transfer from the amine unit, a work function reduction of 1.55 eV is achieved, resulting in a less deep Fermi level. This explanation is not likely to hold for the technologically more relevant procedure on which we shall focus, being the deposition of WMLs from solution on a metal at atmospheric pressure: the metal is not atomically clean, which likely inhibits chemisorption. In other work by Zhou et al. [ 13 ] it is shown that the work function reduction, at atmospheric pressure, by the amine groups in poly(ethylenimine ethoxylated) (PEIE), is generally the same on different conductors. Work function modifi cation by polyelectrolytes and tertiary aliphatic amines is found to be due to the formation of a net dipole at the electrode interface, induced by interaction with its own image dipole in the electrode. In polyelectrolytes differences in size and side groups between the moving ions lead to differences in approach distance towards the surface. These differences determine magnitude and direction of the resulting dipole. In tertiary aliphatic amines the lone pairs of electrons are anticipated to shift towards their image when close to the interface rather than the nitrogen nuclei, which are sterically hindered by the alkyl side chains. ...

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“…Recently, transition metal oxides (TMOs) [1,2], such molybdenum trioxide (MoO 3 ) [3], tungsten oxide (WO 3 ) [4], vanadium pentoxide (V 2 O 5 ) [5] and rhenium trioxide (ReO 3 ) [6], have gained great attention because of their wide applications in optoelectronic devices composed of organic semiconductors (OSs). For example, in organic light-emitting diodes (OLEDs) [7], they are used as anode modification interlayers [3], which can substantially reduce the hole injection barrier.…”

Section: Introductionmentioning

confidence: 99%

Transition metal oxides on organic semiconductors

Zhao

Zhang

Liu

et al. 2014

Organic Electronics

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a b s t r a c tTransition metal oxides (TMOs) on organic semiconductors (OSs) structure has been widely used in inverted organic optoelectronic devices, including inverted organic light-emitting diodes (OLEDs) and inverted organic solar cells (OSCs), which can improve the stability of such devices as a result of improved protection of air sensitive cathode. However, most of these reports are focused on the anode modification effect of TMO and the nature of TMO-on-OS is not fully understood. Here we show that the OS on TMO forms a two-layer structure, where the interface mixing is minimized, while for TMO-on-OS, due to the obvious diffusion of TMO into the OS, a doping-layer structure is formed. This is evidenced by a series of optical and electrical studies. By studying the TMO diffusion depth in different OS, we found that this process is governed by the thermal property of the OS. The TMO tends to diffuse deeper into the OS with a lower evaporation temperature. It is shown that the TMO can diffuse more than 20 nm into the OS, depending on the thermal property of the OS. We also show that the TMO-on-OS structure can replace the commonly used OS with TMO doping structure, which is a big step toward in simplifying the fabrication process of the organic optoelectronic devices.

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Electronic structure of Vanadium pentoxide: An efficient hole injector for organic electronic materials

Cited by 243 publications

References 35 publications

Quasiparticle self-consistentGWcalculations of the electronic band structure of bulk and monolayerV2O5

Quasiparticle self-consistentGWcalculations of the electronic band structure of bulk and monolayerV2O5

Origin of Work Function Modification by Ionic and Amine‐Based Interface Layers

Transition metal oxides on organic semiconductors

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