Binding Modes of Fluorinated Benzylphosphonic Acids on the Polar ZnO Surface and Impact on Work Function

Wood, Christopher A.; Li, Hong; Winget, Paul; Brédas, Jean‐Luc

doi:10.1021/jp3050725

Cited by 59 publications

(113 citation statements)

References 104 publications

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“…[2,23,24] In this case, the hole injection current remains constant even if the electrode WF exceeds the ionization energy of OSCs. [19,25] This is well shown in Figure 4, where the hole injection current becomes independent of the ZnO WF above 4.8 eV, which is close to P3HT ionization energy. [26] Surprisingly, hole injection from untreated ZnO (prepared in the dark) is inefficient, despite its fairly high WF of 4.7 eV.…”

Section: Resultssupporting

confidence: 62%

“…Herein, we found that UV light soaking decreases the WF regardless of whether the ZnO surface is additionally modified with an SAM. It has been shown that PA molecules, as used in this study undergo tridentate binding to the ZnO surface, meaning that each PA molecule occupies three surface sites. The fact that the presence of the SAM does not reduce the strength of the light‐induced WF shift suggests that this phenomenon is not entirely caused by changes of the ZnO surface chemistry, but may also involve internal surfaces such as grain boundaries .…”

Section: Resultsmentioning

confidence: 99%

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Simultaneous Effect of Ultraviolet Radiation and Surface Modification on the Work Function and Hole Injection Properties of ZnO Thin Films

Raoufi

Hörmann

Ligorio

et al. 2020

Physica Status Solidi (a)

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The combined effect of ultraviolet (UV) light soaking and self‐assembled monolayer deposition on the work function (WF) of thin ZnO layers and on the efficiency of hole injection into the prototypical conjugated polymer poly(3‐hexylthiophen‐2,5‐diyl) (P3HT) is systematically investigated. It is shown that the WF and injection efficiency depend strongly on the history of UV light exposure. Proper treatment of the ZnO layer enables ohmic hole injection into P3HT, demonstrating ZnO as a potential anode material for organic optoelectronic devices. The results also suggest that valid conclusions on the energy‐level alignment at the ZnO/organic interfaces may only be drawn if the illumination history is precisely known and controlled. This is inherently problematic when comparing electronic data from ultraviolet photoelectron spectroscopy (UPS) measurements carried out under different or ill‐defined illumination conditions.

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Section: Resultssupporting

confidence: 62%

Section: Resultsmentioning

confidence: 99%

Simultaneous Effect of Ultraviolet Radiation and Surface Modification on the Work Function and Hole Injection Properties of ZnO Thin Films

Raoufi

Hörmann

Ligorio

et al. 2020

Physica Status Solidi (a)

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“…13 After surface modification (Figure 2b−d), the two initial components (bulk oxygen and surface−OH) are markedly decreased. Furthermore, the O 1s spectrum of each SAMmodified ZnO surface can be fitted with three additional components, which were previously assigned on the basis of their binding energy shifts (with respect to the bulk oxygen) to two different PA binding modes, 13,25 i.e., bidentate and tridentate binding (red and blue components in Figure 2b−d). Table 1 summarizes the binding energies of the O 1s core levels for the three SAM-modified ZnO surfaces.…”

Section: Resultsmentioning

confidence: 99%

Energy-Level Engineering at ZnO/Oligophenylene Interfaces with Phosphonate-Based Self-Assembled Monolayers

Timpel

Nardi

Ligorio

et al. 2015

ACS Appl. Mater. Interfaces

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We used aromatic phosphonates with substituted phenyl rings with different molecular dipole moments to form self-assembled monolayers (SAMs) on the Zn-terminated ZnO(0001) surface in order to engineer the energy-level alignment at hybrid inorganic/organic semiconductor interfaces, with an oligophenylene as organic component. The work function of ZnO was tuned over a wide range of more than 1.7 eV by different SAMs. The difference in the morphology and polarity of the SAMmodified ZnO surfaces led to different oligophenylene orientation, which resulted in an orientation-dependent ionization energy that varied by 0.7 eV. The interplay of SAM-induced work function modification and oligophenylene orientation changes allowed tuning of the offsets between the molecular frontier energy levels and the semiconductor band edges over a wide range. Our results demonstrate the versatile use of appropriate SAMs to tune the energy levels of ZnO-based hybrid semiconductor heterojunctions, which is important to optimize its function, e.g., targeting either interfacial energy-or chargetransfer.

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“…[1][2][3] These properties together with a type-I level alignment at the hybrid interface would be ideally suited for light-emitting applications. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] The adsorption of a molecular layer on inorganic surfaces has also been exploited to tune the work function of the inorganic component. [6][7][8][9][10] Prerequisite for that is the lightinduced creation of hybrid or charge-transfer excitons, which exhibit the hole to a large extent on one side of the interface while the excited electron would reside on the other side.…”

Section: Introductionmentioning

confidence: 99%

Electronic and Optical Excitations at the Pyridine/ZnO(101¯0) Hybrid Interface

Turkina

Nabok

Guļāns

et al. 2018

Advcd Theory and Sims

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By combining all-electron density-functional theory with many-body perturbation theory, a prototypical inorganic/organic hybrid system, composed of pyridine molecules that are chemisorbed on the nonpolar ZnO(1010) surface is investigated. The G 0 W 0 approximation is employed to describe its one-particle excitations in terms of the quasiparticle band structure, and the Bethe-Salpeter equation is solved to obtain the absorption spectrum. The different character of the constituents leads to very diverse self-energy corrections of individual Kohn-Sham states, and thus the G 0 W 0 band structure is distinctively different from its DFT counterpart, that is, many-body effects cannot be regarded as a rigid shift of the conduction bands. The nature of the optical excitations at the interface over a wide energy range is explored and it is shown that various kinds of electron-hole pairs are formed, comprising hybrid excitons and (hybrid) charge-transfer excitations. The absorption onset is characterized by a strongly bound brightZnO-dominated hybrid exciton. For the selected examples of either exciton type, the individual contributions from the valence and conduction bands are analyzed and the binding strength and extension of the electron-hole wavefunctions are discussed.

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Binding Modes of Fluorinated Benzylphosphonic Acids on the Polar ZnO Surface and Impact on Work Function

Cited by 59 publications

References 104 publications

Simultaneous Effect of Ultraviolet Radiation and Surface Modification on the Work Function and Hole Injection Properties of ZnO Thin Films

Simultaneous Effect of Ultraviolet Radiation and Surface Modification on the Work Function and Hole Injection Properties of ZnO Thin Films

Energy-Level Engineering at ZnO/Oligophenylene Interfaces with Phosphonate-Based Self-Assembled Monolayers

Electronic and Optical Excitations at the Pyridine/ZnO(101¯0) Hybrid Interface

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