A highly enhanced photoelectrochemical performance of BiVO4 photoanodes modified with CoPi groups by increasing energy band bending, accelerating hole separation and improving water oxidation kinetics

BiVO4 is one of the most attractive photoanode materials for photoelectrochemical water splitting. Herein, cobalt phosphate (CoPi) modified BiVO4 (BiVO4/CoPi) photoanode is prepared by electrodeposition. The physical and chemical characterization...

Localized Energy Band Bending in ZnO Nanorods Decorated with Au Nanoparticles

Surface decoration by means of metal nanostructures is an effective way to locally modify the electronic properties of materials. The decoration of ZnO nanorods by means of Au nanoparticles was experimentally investigated and modelled in terms of energy band bending. ZnO nanorods were synthesized by chemical bath deposition. Decoration with Au nanoparticles was achieved by immersion in a colloidal solution obtained through the modified Turkevich method. The surface of ZnO nanorods was quantitatively investigated by Scanning Electron Microscopy, Transmission Electron Microscopy and Rutherford Backscattering Spectrometry. The Photoluminescence and Cathodoluminescence of bare and decorated ZnO nanorods were investigated, as well as the band bending through Mott–Schottky electrochemical analyses. Decoration with Au nanoparticles induced a 10 times reduction in free electrons below the surface of ZnO, together with a decrease in UV luminescence and an increase in visible-UV intensity ratio. The effect of decoration was modelled with a nano-Schottky junction at ZnO surface below the Au nanoparticle with a Multiphysics approach. An extensive electric field with a specific halo effect formed beneath the metal–semiconductor interface. ZnO nanorod decoration with Au nanoparticles was shown to be a versatile method to tailor the electronic properties at the semiconductor surface.

Polarization-Charge Inversion at Al2O3/GaN Interfaces through Post-Deposition Annealing

The effects of post-deposition annealing (PDA) on the formation of polarization-charge inversion at ultrathin Al2O3/Ga-polar GaN interfaces are assessed by the analysis of energy band bending and measurement of electrical conduction. The PDA-induced positive interface charges form downward energy band bending at the Al2O3/GaN interfaces with polarization-charge inversion, which is analyzed using X-ray photoelectron spectroscopy. Net charge and interface charge densities at the Al2O3/GaN interfaces are estimated after PDA at 500 °C, 700 °C, and 900 °C. The PDA temperatures affect the formation of charge densities. That is, the charge density increases up to 700 °C and then decreases at 900 °C. Electrical characteristics of GaN Schottky diodes with ultrathin Al2O3 layers exhibit the passivation ability of the Al2O3 surface layer and the effects of polarization-charge inversion through PDA. This result can be applied to improvement in GaN-based electronic devices where surface states and process temperature work important role in device performance.

Ultrathin Hematite Photoanode with Gradient Ti Doping

The poor photoelectrochemical (PEC) performance derived from insufficient charge separation in hematite photoanode crucially limits its application. Gradient doping with band bending in a large region is then considered as a promising strategy, facilitating the charge transfer ability due to the built-in electric field. Herein, we developed a synthetic strategy to prepare gradient Ti-doped ultrathin hematite photoelectrode and systematically investigated its PEC performance. The as-synthesized electrode (1.5-6.0% doping level from the surface to the substrate) delivered a photocurrent of about 1.30 mA cm-2 at 1.23 V versus the reversible hydrogen electrode (RHE), which is nearly 100% higher than that of homogeneously doped hematite electrode. The enhanced charge transfer property, induced by the energy band bending due to the built-in electric field, has been further confirmed by electrochemical measurements. This strategy of gradient doping should be adaptable and can be applied for other functional materials in various fields.

Interfacial engineering of a ZnO electron transporting layer using self-assembled monolayers for high performance and stable perovskite solar cells

The SAM layer which formed hydrogen-bonding to the methylammonium of the perovskite induced dipole moments at the interface, resulting in energy band bending and increased built-in voltage, and consequently, improved charge transfer of the PSC.

Определение параметров структур металл-диэлектрик- полупроводник со сверхтонким изолирующим слоем из высокочастотных вольт-фарадных характеристик

A simple numerical method for processing the data of the high-frequency capacitance–voltage characteristics of metal–insulator–semiconductor structures is proposed. The approach is based on analyzing the experimental characteristics near the flat-band states, where the charge exchange of surface localized electron states is of little importance compared with changes in the near-boundary charged layer in the semiconductor. The developed technique makes it possible, first, to find the necessary parameters of the semiconductor and insulating layer and, second, to obtain the experimental field dependences of the energy-band bending in the semiconductor and the total concentration of the built-in charge, the charge of boundary states and minority charge carriers at the semiconductor–insulator interface in the range from the flat bands to deep depletion. The technique is well applicable to structures with an ultra-thin insulating layer. On n -Si-based metal–oxide–semiconductor samples with an oxide thickness of 39 Å, experimental approbation of the proposed approach is carried out. The accuracy of the obtained results is 2–3%.