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Modification of TiO <sub/>2</sub> (1?1?0)/organic hole transport layer interface energy levels by a dipolar perylene derivative
摘要： Our photoemission study reveals that the work function of TiO2(1 1 0) decreases by up to 1.5 eV upon deposition of 9-(bis-(p-(tert-octyl)phenyl)amino)-perylene-3,4-dicarboxylic anhydride (BOPA-PDCA). This effect is attributed to a chemical reaction of TiO2(1 1 0) and the molecular anhydride group, as well as the molecular dipole. Analysis of the film thickness dependent photoemission and metastable atom electron spectroscopy data reveals that for low coverage the perylene backbone of BOPA-PDCA is almost parallel to the substrate surface and higher coverage leads to an orientational transition to essentially upright standing molecules. Comparing the energy-level alignment between TiO2(1 1 0) and the hole transport materials N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) without and with the BOPA-PDCA interlayer, we find that the perylene derivative has a positive impact on the level alignment for dye-sensitized solar cells with high open-circuit voltages.
关键词： solid state dye-sensitized solar cell,titanium dioxide,energy-level alignment,ultraviolet photoelectron spectroscopy,metastable atom electron spectroscopy,perylene
更新于2025-09-23 15:23:52
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Valence band behaviour of zirconium oxide, Photoelectron and Auger spectroscopy study
摘要： In this study X-ray Photoelectron Spectroscopy and Ultraviolet Photoelectron Spectroscopy were combined to investigate the effect of oxygen incorporation on the valence band behaviour of ZrOx. The Auger transitions involving valence bands are found to mimic the self-folded density of state measured using Ultraviolet Photoelectron Spectroscopy. The valence band once constructed in a sub-oxide form, stays at a fixed energy position despite the change in the stoichiometry. This behaviour is found to be useful in setting a reference for X-ray Photoelectron Spectroscopy charge correction. The results of the charged corrected spectra were compared to other methods and found to be in great agreement. Finally, a correlation between the core-level binding energy and the structural property of ZrOx is given.
关键词： valence band,Ultraviolet Photoelectron Spectroscopy,X-ray Photoelectron Spectroscopy,Photoelectron,zirconium oxide,Auger spectroscopy
更新于2025-09-23 15:21:01
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Crystalline structure, electronic and lattice-dynamics properties of NbTe2
摘要： Layered-structure materials are currently relevant given their quasi-2D nature. Knowledge of their physical properties is currently of major interest. Niobium ditelluride possesses a monoclinic layered-structure with a distortion in the tellurium planes. This structural complexity has hindered the determination of its fundamental physical properties. In this work, NbTe2 crystals were used to elucidate its structural, compositional, electronic and vibrational properties. These findings have been compared with calculations based on density functional theory. The chemical composition and elemental distribution at the nanoscale were obtained through atom probe tomography. Ultraviolet photoelectron spectroscopy allowed the first determination of the work function of NbTe2. Its high value, 5.32 eV, and chemical stability allow foreseeing applications such as contact in optoelectronics. Raman spectra were obtained using different excitation laser lines: 488, 633, and 785 nm. The vibrational frequencies were in agreement with those determined through density functional theory. It was possible to detect a theoretically-predicted, low-frequency, low-intensity Raman active mode not previously observed. The dispersion curves and electronic band structure were calculated, along with their corresponding density of states. The electrical properties, as well as a pseudo-gap in the density of states around the Fermi energy are characteristics proper of a semi metal.
关键词： Electronic band structure,Ultraviolet photoelectron spectroscopy,Density functional theory,Atom probe tomography,Niobium ditelluride,Layered-structure materials,Raman spectra,Density of states,Semimetal
更新于2025-09-23 15:21:01