Abstract
Gallium-doped zinc oxide (GZO) surfaces, both bare and modified with chemisorbed phosphonic acid (PA) molecules, are studied using a combination of density functional theory calculations and ultraviolet and X-ray photoelectron spectroscopy measurements. Excellent agreement between theory and experiment is obtained, which leads to an understanding of: i) the core-level binding energy shifts of the various oxygen atoms belonging to different surface sites and to the phosphonic acid molecules; ii) the GZO work-function change upon surface modification, and; iii) the energy level alignments of the frontier molecular orbitals of the PA molecules with respect to the valence band edge and Fermi level of the GZO surface. Importantly, both density of states calculations and experimental measurements of the valence band features demonstrate an increase in the density of states and changes in the characteristics of the valence band edge of GZO upon deposition of the phosphonic acid molecules. The new valence band features are associated with contributions from surface oxygen atoms near a defect site on the oxide surface and from the highest occupied molecular orbitals of the phosphonic acid molecules. The surface modifications of gallium-doped zinc oxide with a series of self-assembled phosphonic acid monolayers are investigated. Excellent agreement is obtained between theoretical and experimental results regarding the surface work-function modification, the O 1s core-level binding energy shifts, and the enery level alignment between the highest occupied molecular orbitals of the modifiers and the valence band maximum of the surface.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 3593-3603 |
| Number of pages | 11 |
| Journal | Advanced Functional Materials |
| Volume | 24 |
| Issue number | 23 |
| DOIs | |
| State | Published - Jun 18 2014 |
Fingerprint
Keywords
- density functional theory
- energy-level alignments
- metal oxides
- organic photovoltaics
- surface modifications
- ultraviolet photoelectron spectroscopy
ASJC Scopus subject areas
- Biomaterials
- Electrochemistry
- Condensed Matter Physics
- Electronic, Optical and Magnetic Materials
Cite this
Modification of the gallium-doped zinc oxide surface with self-assembled monolayers of phosphonic acids : A joint theoretical and experimental study. / Li, Hong; Ratcliff, Erin L; Sigdel, Ajaya K.; Giordano, Anthony J.; Marder, Seth R.; Berry, Joseph J.; Brédas, Jean Luc.
In: Advanced Functional Materials, Vol. 24, No. 23, 18.06.2014, p. 3593-3603.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Modification of the gallium-doped zinc oxide surface with self-assembled monolayers of phosphonic acids
T2 - A joint theoretical and experimental study
AU - Li, Hong
AU - Ratcliff, Erin L
AU - Sigdel, Ajaya K.
AU - Giordano, Anthony J.
AU - Marder, Seth R.
AU - Berry, Joseph J.
AU - Brédas, Jean Luc
PY - 2014/6/18
Y1 - 2014/6/18
N2 - Gallium-doped zinc oxide (GZO) surfaces, both bare and modified with chemisorbed phosphonic acid (PA) molecules, are studied using a combination of density functional theory calculations and ultraviolet and X-ray photoelectron spectroscopy measurements. Excellent agreement between theory and experiment is obtained, which leads to an understanding of: i) the core-level binding energy shifts of the various oxygen atoms belonging to different surface sites and to the phosphonic acid molecules; ii) the GZO work-function change upon surface modification, and; iii) the energy level alignments of the frontier molecular orbitals of the PA molecules with respect to the valence band edge and Fermi level of the GZO surface. Importantly, both density of states calculations and experimental measurements of the valence band features demonstrate an increase in the density of states and changes in the characteristics of the valence band edge of GZO upon deposition of the phosphonic acid molecules. The new valence band features are associated with contributions from surface oxygen atoms near a defect site on the oxide surface and from the highest occupied molecular orbitals of the phosphonic acid molecules. The surface modifications of gallium-doped zinc oxide with a series of self-assembled phosphonic acid monolayers are investigated. Excellent agreement is obtained between theoretical and experimental results regarding the surface work-function modification, the O 1s core-level binding energy shifts, and the enery level alignment between the highest occupied molecular orbitals of the modifiers and the valence band maximum of the surface.
AB - Gallium-doped zinc oxide (GZO) surfaces, both bare and modified with chemisorbed phosphonic acid (PA) molecules, are studied using a combination of density functional theory calculations and ultraviolet and X-ray photoelectron spectroscopy measurements. Excellent agreement between theory and experiment is obtained, which leads to an understanding of: i) the core-level binding energy shifts of the various oxygen atoms belonging to different surface sites and to the phosphonic acid molecules; ii) the GZO work-function change upon surface modification, and; iii) the energy level alignments of the frontier molecular orbitals of the PA molecules with respect to the valence band edge and Fermi level of the GZO surface. Importantly, both density of states calculations and experimental measurements of the valence band features demonstrate an increase in the density of states and changes in the characteristics of the valence band edge of GZO upon deposition of the phosphonic acid molecules. The new valence band features are associated with contributions from surface oxygen atoms near a defect site on the oxide surface and from the highest occupied molecular orbitals of the phosphonic acid molecules. The surface modifications of gallium-doped zinc oxide with a series of self-assembled phosphonic acid monolayers are investigated. Excellent agreement is obtained between theoretical and experimental results regarding the surface work-function modification, the O 1s core-level binding energy shifts, and the enery level alignment between the highest occupied molecular orbitals of the modifiers and the valence band maximum of the surface.
KW - density functional theory
KW - energy-level alignments
KW - metal oxides
KW - organic photovoltaics
KW - surface modifications
KW - ultraviolet photoelectron spectroscopy
UR - http://www.scopus.com/inward/record.url?scp=84902381777&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84902381777&partnerID=8YFLogxK
U2 - 10.1002/adfm.201303670
DO - 10.1002/adfm.201303670
M3 - Article
AN - SCOPUS:84902381777
VL - 24
SP - 3593
EP - 3603
JO - Advanced Materials for Optics and Electronics
JF - Advanced Materials for Optics and Electronics
SN - 1057-9257
IS - 23
ER -