Photoemission study of C60-induced barrier reduction for hole injection at N, N′-bis(naphthalene-1-y1)-N, N′-bis(phenyl) benzidine/Al

Xie, Zuoti; Bao, Ding; Gao, Xiang; You, YinTao; Sun, Zhengyi; Zhang, W. H.; Ding, Xinyi; Hou, X. Y.

doi:10.1063/1.3117831

Cited by 6 publications

(4 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…So, from this analysis, we conclude that the metalÀS bond dipoles are mainly responsible for ΔΦ. This picture is consistent not only with previous findings on the local origin of ΔΦ 44 by photoelectron spectroscopy (suggesting that dipole layers at organicÀmetal interfaces could be formed within a few angstroms from the surface 76,77 ) but also with a standard Helmholtz description and our quantum chemical calculations, which we present next.…”

Section: Resultssupporting

confidence: 93%

“…This picture is not only consistent with previous findings on the local origin of  44 by photoelectron spectroscopy (suggesting that dipole layers at organic-metal 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 interfaces could be formed within a few Å from the surface 76,77 ), but also with a standard Helmholtz description and our quantum chemical calculations, which we present next.…”

Section: Basic Working Equationsmentioning

confidence: 99%

See 1 more Smart Citation

Experimental and Theoretical Analysis of Nanotransport in Oligophenylene Dithiol Junctions as a Function of Molecular Length and Contact Work Function

et al. 2015

View full text Add to dashboard Cite

We report the results of an extensive investigation of metal-molecule-metal tunnel junctions based on oligophenylene dithiols (OPDs) bound to several types of electrodes (M1-S-(C6H4)n-S-M2, with 1 ≤ n ≤ 4 and M1,2 = Ag, Au, Pt) to examine the impact of molecular length (n) and metal work function (Φ) on junction properties. Our investigation includes (1) measurements by scanning Kelvin probe microscopy of electrode work function changes (ΔΦ = ΦSAM - Φ) caused by chemisorption of OPD self-assembled monolayers (SAMs), (2) measurements of junction current-voltage (I-V) characteristics by conducting probe atomic force microscopy in the linear and nonlinear bias ranges, and (3) direct quantitative analysis of the full I-V curves. Further, we employ transition voltage spectroscopy (TVS) to estimate the energetic alignment εh = EF - EHOMO of the dominant molecular orbital (HOMO) relative to the Fermi energy EF of the junction. Where photoelectron spectroscopy data are available, the εh values agree very well with those determined by TVS. Using a single-level model, which we justify via ab initio quantum chemical calculations at post-density functional theory level and additional UV-visible absorption measurements, we are able to quantitatively reproduce the I-V measurements in the whole bias range investigated (∼1.0-1.5 V) and to understand the behavior of εh and Γ (contact coupling strength) extracted from experiment. We find that Fermi level pinning induced by the strong dipole of the metal-S bond causes a significant shift of the HOMO energy of an adsorbed molecule, resulting in εh exhibiting a weak dependence with the work function Φ. Both of these parameters play a key role in determining the tunneling attenuation factor (β) and junction resistance (R). Correlation among Φ, ΔΦ, R, transition voltage (Vt), and εh and accurate simulation provide a remarkably complete picture of tunneling transport in these prototypical molecular junctions.

show abstract

Section: Resultssupporting

confidence: 93%

Section: Basic Working Equationsmentioning

confidence: 99%

Experimental and Theoretical Analysis of Nanotransport in Oligophenylene Dithiol Junctions as a Function of Molecular Length and Contact Work Function

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Injection-limited current would be expected for the pristine metal-organic interface, given the high nominal injection barrier of >1 eV between the work function of the Al electrode (3.6-4.3 eV) and the HOMO level of NPB (≈ 5.4 eV) [11,[59][60][61][62]. The additional interfacial MoO 3 layer, however, not only serves as an electron blocking layer but also improves hole injection into the organic semiconductor.…”

Section: Resultsmentioning

confidence: 99%

Injection-limited and space charge-limited currents in organic semiconductor devices with nanopatterned metal electrodes

2022

View full text Add to dashboard Cite

Charge injection at metal-organic interfaces often limits the electric current in organic light-emitting diodes without additional injection layers. Integrated nanopatterned electrodes may provide a way to overcome this current injection limit by local field enhancements leading to locally space charge–limited currents. We compare electrical characteristics of planar and nanopatterned hole-only devices based on the charge transport material NPB with different thicknesses in order to investigate the nanopattern’s effect on the current limitation mechanism. Integration of a periodic nanograting into the metal electrode yields a current increase of about 1.5 to 4 times, depending on thickness and operating voltage. To verify the experimental results, we implement a finite element simulation model that solves the coupled Poisson and driftdiffusion equations in a weak form. It includes space charges, drift and diffusion currents, non-linear mobility, and charge injection at the boundaries. We find in experiment and simulation that the planar devices exhibit injection-limited currents, whereas the currents in the nanopatterned devices are dominated by space charge effects, overcoming the planar injection limit. The simulations show space charge accumulations at the corners of the nanopattern, confirming the idea of locally space charge–limited currents.

show abstract

“…In this case, the deposition of up to a ML of C 60 F 48 induces an increase in the work function by 1.85 eV and a shift in the ZnTPP HOMO of 0.67 eV. These large energy level shifts originate in the substantial charge transfer at the interface between C 60 F 48 and ZnTPP that occurs due to the fact that EA of C 60 F 48 (molecular form 4.06 eV, 23 solid form 5.0-5.27 eV 23,24 ) exceeds the work function of the bare ZnTPP film, 25 as shown in the energy level diagram in Figure 1(d). Therefore, it is energetically beneficial for electrons to transfer from ZnTPP to C 60 F 48 and the work function increases on account of the electrostatic dipole potential established across the ZnTPP-C 60 F 48 interface by the separated charges.…”

Section: Resultsmentioning

confidence: 99%

Charge-induced distortion and stabilization of surface transfer doped porphyrin films

Smets

Stark

Lach

et al. 2013

The Journal of Chemical Physics

View full text Add to dashboard Cite

The interaction between zinc-tetraphenylporphyrin (ZnTPP) and fullerenes (C 60 and C 60 F 48 ) are studied using ultraviolet photoelectron spectroscopy (UPS) and scanning tunneling microscopy (STM). Low temperature STM reveals highly ordered ZnTPP monolayers on Au(111). In contrast to C 60 , a submonolayer coverage of C 60 F 48 results in long-range disorder of the underlying single ZnTPP layer and distortion of individual ZnTPP molecules. This is induced by substantial charge transfer at the organic-organic interface, revealed by the interface energetics from UPS. However, a second layer of ZnTPP prevents C 60 F 48 guests from breaking the self-assembled porphyrin template. This finding is important for understanding the growth behaviour of "bottom-up" functional nanostructures involving strong donor-acceptor heterojunctions in molecular electronics. © 2013 AIP Publishing LLC. [http://dx

show abstract

Photoemission study of C60-induced barrier reduction for hole injection at N, N′-bis(naphthalene-1-y1)-N, N′-bis(phenyl) benzidine/Al

Cited by 6 publications

References 16 publications

Experimental and Theoretical Analysis of Nanotransport in Oligophenylene Dithiol Junctions as a Function of Molecular Length and Contact Work Function

Experimental and Theoretical Analysis of Nanotransport in Oligophenylene Dithiol Junctions as a Function of Molecular Length and Contact Work Function

Injection-limited and space charge-limited currents in organic semiconductor devices with nanopatterned metal electrodes

Charge-induced distortion and stabilization of surface transfer doped porphyrin films

Contact Info

Product

Resources

About