Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

Proceedings of SPIE - The International Society for Optical Engineering

Enabling Flexible All-Perovskite Tandem Solar Cells

Scanning electrochemical cell microscopy (SECCM) is a new pipette-based imaging technique purposely designed to allow simultaneous electrochemical, conductance, and topographical visualization of surfaces and interfaces. SECCM uses a tiny meniscus or droplet, at the end of a double-barreled (theta) pipette, for high-resolution functional imaging and nanoscale electrochemical measurements. Here we introduce this technique and provide an overview of its principles, instrumentation, and theory. We discuss the power of SECCM in resolving complex structure-activity problems and provide considerable new information on electrode processes by referring to key example systems, including graphene, graphite, carbon nanotubes, nanoparticles, and conducting diamond. The many longstanding questions that SECCM has been able to answer during its short existence demonstrate its potential to become a major technique in electrochemistry and interfacial science.

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Scanning Electrochemical Cell Microscopy: A Versatile Technique for Nanoscale Electrochemistry and Functional Imaging

MOF-derived N-doped carbon bubbles on carbon tube arrays for flexible high-rate supercapacitors

Chemical etching is widely applied to texture the surface of sputter-deposited zinc oxide for light scattering in thin-film silicon solar cells. Based on experimental findings from the literature and our own results we propose a model that explains the etching behavior of ZnO depending on the structural material properties and etching agent. All grain boundaries are prone to be etched to a certain threshold, that is defined by the deposition conditions and etching solution. Additionally, several approaches to modify the etching behavior through special preparation and etching steps are provided.

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Chemical etching of zinc oxide for thin-film silicon solar cells.

Magnetron sputtered aluminum-doped zinc oxide (ZnO:Al) is used as a window layer in silicon-based thin-film solar cells due to its high transparency, high conductivity, and ability to provide effective light trapping after etching in a dilute HCl solution. A challenge with this method is the strong influence of sputtering conditions on the density and shape of the ZnO:Al etch features. Here we present a novel chemical etch process based on HF that enables the modification of surface features through the etch process itself, thus allowing the separate optimization of ZnO:Al deposition and texturization. The different etch characteristics of HCl and HF are studied on single crystal ZnO. Using the different etch characteristics of HF we effectively texturize polycrystalline ZnO:Al films which previously exhibited only poor light trapping in silicon thin-film solar cells. The light trapping improvement is seen by an 18% increase in short circuit current density when used in microcrystalline silicon solar cells. Additionally, using mixtures of HCl and HF we are able to tune the feature size and shape on a given ZnO:Al sample.

Scanning electron microscope images of high-rate deposited ZnO:Al etched in HCl and HF.

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Novel etch process to tune crater size on magnetron sputtered ZnO:Al

A novel approach is presented for introducing a surface morphology with beneficial light scattering properties to sputterdeposited ZnO:Al films, being used as front contact in Si thin film photovoltaic devices. Electrochemical anodization was used to trigger local corrosion, leading to interfacial structures complementary to those commonly prepared by an etching step in diluted HCl. By systematic variation of electrochemical etching conditions and electrolytes, sensible experimental parameters were evaluated for the preparation of ZnO films that can be applied in Si thin film solar cells. The prepared films were characterized by scanning electron microscopy, four-point resistance and Hall measurements. Furthermore, the kinetics of the heterogeneous interfacial reaction during the corrosion process were studied utilizing electroanalytical techniques. This allowed the identification of the processes occurring at the solid/liquid interface. Application of such films in microcrystalline Si single junction solar cells has shown promising initial results.

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Electrochemical etching of zinc oxide for silicon thin film solar cell applications

The processes during chemical and electrochemical etching of Al-doped ZnO are investigated utilizing a scanning flow cell setup with online detection of dissolved Zn ions. The rate of chemical dissolution was found to be a linear function of buffer and proton concentration in near neutral pH solutions according to a transport limited reaction. In contrast, electrochemical etching is limited by the kinetics of the reaction and increases linearly with the imposed current density. Due to this fundamental difference, the dissolution of Zn can be either uniform over the whole surface or highly localized at active sites like grain boundaries. A combined approach of chemical etching and the well-controllable galvanostatic dissolution thus allows a fine adjustment of the ZnO:Al surface texture for applications in silicon thin film photovoltaic cells in order to improve their overall energy conversion efficiency.

Sascha E. Pust

Papers

Chemical etching of zinc oxide for thin-film silicon solar cells.

Novel etch process to tune crater size on magnetron sputtered ZnO:Al

Electrochemical etching of zinc oxide for silicon thin film solar cell applications

Electrochemical texturing of Al-doped ZnO thin films for photovoltaic applications

Light induced hydrogen generation with silicon-based thin film tandem solar cells used as photocathode