BHJ solar cells are typically fabricated with a transparent conductive anode (e.g. indium tin oxide, ITO), a low-work-function metal cathode (e.g., Al, Ca), and an active layer (a mixture of conjugated polymer and fullerene derivative) sandwiched between the anode and cathode. The BHJ layer and cathode dramatically affect the stability. In particular, the cathode is susceptible to degradation by oxygen and water vapor. Poly(3,4ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is often used as an anode buffer layer. Long-term stability is a problem because PEDOT:PSS is hygroscopic and acidic. [ 17–21 ]

Inverted Polymer Solar Cells Integrated with a Low‐Temperature‐Annealed Sol‐Gel‐Derived ZnO Film as an Electron Transport Layer

Oxygen vacancies in crystal have important impacts on the electronic properties of ZnO. With ZnO2 as precursors, we introduce a high concentration of oxygen vacancies into ZnO successfully. The obtained ZnO exhibits a yellow color, and the absorption edge shifts to longer wavelength. Raman and XPS spectra reveal that the concentration of oxygen vacancies in the ZnO decreased when the samples are annealed at higher temperature in air. It is consistent with the theory calculation. The increasing of oxygen vacancies results in a narrowing bandgap and increases the visible light absorption of the ZnO. The narrowing bandgap can be confirmed by the enhancement of the photocurrent response when the ZnO was irradiated with visible light. The ZnO with oxygen vacancies are found to be efficient for photodecomposition of 2,4-dichlorophenol under visible light irradiation.

Oxygen vacancy induced band-gap narrowing and enhanced visible light photocatalytic activity of ZnO.

A facile and general method has been developed to fabricate oxygen vacancies on perovskite SrTiO3 (STO) nanocrystals through a controllable solid-state reaction of NaBH4 and SrTiO3 nanocrystals. STO samples with tunable color, oxygen vacancy concentration on nanocrystal surface have been synthesized. TEM results reveal that these STO samples have a crystalline core/amorphous shell structure (SrTiO3@SrTiO3–x). XPS and EPR results disclose that the oxygen vacancy concentration increases with the increase of reaction time and temperature. The concentration of oxygen vacancies calculated from TGA data, could reach 5.07% (atom) in this study. UV–vis spectra and photocatalytic results indicate that oxygen vacancies on STO surface play an important role in influencing the light absorption and photocatalytic performance. However, an excess amount of oxygen vacancies leads to a decrease of photocatalytic performance. The optimal photocatalytic activity for H2 production under UV–vis irradiation is up to 2.2 mmol h...

Oxygen Vacancy Enhanced Photocatalytic Activity of Pervoskite SrTiO3

Band gap narrowing is important and advantageous for potential visible light photocatalytic applications involving metal oxide nanostructures. This paper reports a simple biogenic approach for the promotion of oxygen vacancies in pure zinc oxide (p-ZnO) nanostructures using an electrochemically active biofilm (EAB), which is different from traditional techniques for narrowing the band gap of nanomaterials. The novel protocol improved the visible photocatalytic activity of modified ZnO (m-ZnO) nanostructures through the promotion of oxygen vacancies, which resulted in band gap narrowing of the ZnO nanostructure (Eg = 3.05 eV) without dopants. X-ray diffraction, UV-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy, Raman spectroscopy, photoluminescence spectroscopy and high resolution transmission electron microscopy confirmed the oxygen vacancy and band gap narrowing of m-ZnO. m-ZnO enhanced the visible light catalytic activity for the degradation of different classes of dyes and 4-nitrophenol compared to p-ZnO, which confirmed the band gap narrowing because of oxygen defects. This study shed light on the modification of metal oxide nanostructures by EAB with a controlled band structure.

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Oxygen vacancy induced band gap narrowing of ZnO nanostructures by an electrochemically active biofilm

The effects of annealing environment on the luminescence characteristics of ZnO thin films that were deposited on SiO2/Si substrates by reactive RF magnetron sputtering were investigated by X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL). An analysis of the O 1s peak of ZnO film revealed that the concentration of oxygen vacancies increased with the annealing temperature from 600 °C to 900 °C under an ambient atmosphere. The PL results demonstrated that the intensity of green light emission at 523 nm also increased with temperature. Under various annealing atmospheres, the analyses of PL indicated that only one emission peak (523 nm) was obtained, indicating that only one class of defect was responsible for the green luminescence. The green light emission was strongest and the concentration of oxygen vacancies was highest when the ZnO film was annealed in ambient atmosphere at 900 °C. The results in this investigation show that the luminescence mechanism of the emission of green light from a ZnO thin film is associated primarily with oxygen vacancies.

Luminescence mechanism of ZnO thin film investigated by XPS measurement

X-ray photoelectron spectroscopy and auger electron spectroscopy studies of Al-doped ZnO films

NiCrAlY coatings were prepared on cast Ni-based IN100 superalloy using are ion plating, leading to a dense structure. The surface became smoother after vacuum heat treatment. The oxidation kinetic curves of the IN100 alloy and the coating were obtained. The results indicate that NiCrAlY coating gains more weight after cyclic than after isothermal oxidation and no oxide spallation was evident. The oxidation resistance of IN100 superalloy when exposed to either isothermal or cyclic oxidation was markedly improved by coating with NiCrAlY. The oxide scales mainly consisted of alpha-Al2O3 and Cr2O3, at 900degreesC. In the initial oxidation stage at 1000degreesC, three kinds of oxides, NiO, Cr2O3 and alpha-Al2O3, formed simultaneously. With further oxidation, not only is the thickness of the oxide scale increased, but complex reactions also occurred. (C) 2002 Elsevier Science B.V. All rights reserved.

Oxidation behaviour of NiCrAlY coatings on Ni-based superalloy

ZnO films doped with Al and Mn have been prepared by DC reactive magnetron sputtering at room temperature. The electro-optical, structural properties and compositional analysis of the films have been investigated using Hall-effect measurement, optical spectroscopy, X-ray diffraction, atomic force microscope and Auger electron spectroscopy. A minimum resistivity of 3.46 x 10(-4) Omega cm and more than 80.0% transmittance at 550 nrn have been obtained. It has been observed that the percentages of Al and Mn in the films were slightly lower than that of Al and Mn mixed in the targets. It has been found that all deposited films, which contains compressive stress, have c-axis preferred orientation perpendicular to the substrate with flat and smooth surface (root-mean-square surface roughness is of the order of similar to 3 nm over 5 x 5 mum(2)). In-grain scattering has been suggested to be the most probable scattering mechanism for the films (N> 10(20) cm(-3)) at room temperature. (C) 2003 Elsevier B.V. All rights reserved.

R.F. Huang

Papers

X-ray photoelectron spectroscopy and auger electron spectroscopy studies of Al-doped ZnO films

Oxidation behaviour of NiCrAlY coatings on Ni-based superalloy

Transparent conductive Al and Mn doped ZnO thin films prepared by DC reactive magnetron sputtering

Surface composite nanostructures of AZ91 magnesium alloy induced by high current pulsed electron beam treatment

Oxidation behaviour of the alloy IC-6 and protective coatings