• Energy Research

The combination of oxide and heavier chalcogenide layers in thin film photovoltaics suffers limitations associated with oxygen incorporation and sulfur deficiency in the chalcogenide layer or with a chemical incompatibility which results in dewetting issues and defect states at the interface. Here, we establish atomic layer deposition (ALD) as a tool to overcome these limitations. ALD allows one to obtain highly pure Sb2S3 light absorber layers, and we exploit this technique to generate an additional interfacial layer consisting of 1.5 nm ZnS. This ultrathin layer simultaneously resolves dewetting and passivates defect states at the interface. We demonstrate via transient absorption spectroscopy that interfacial electron recombination is one order of magnitude slower at the ZnS-engineered interface than hole recombination at the Sb2S3/P3HT interface. The comparison of solar cells with and without oxide incorporation in Sb2S3, with and without the ultrathin ZnS interlayer, and with systematically varied Sb2S3 thickness provides a complete picture of the physical processes at work in the devices.

Metagenomic fosmid libraries were constructed from hydrothermal chimneys and fluids and screened for hydrogenase activity by means of an activity-based screen. The hydrogen evolution activity of protein extracts from positively screened clones was determined by means of gas chromatography. For the most active clone (SP11F2) the hydrogen evolution activity was determined at different pH conditions and the stability of the respective enzyme ectract under different storage conditions was tested. The datasets contain hydrogen evolution activities of fosmid clones from the Sisters Peak, Nibelungen and Lilliput hydrothermal vent fields. Metagenomic fosmid libraries were constructed from the environmental sample and screened for hydrogen uptake activity (Adam and Perner 2018). The hydrogen evolution activity of the fosmid clones has been determined as described in the related publication.

Hydrogen can in the future serve as an advantageous carrier of renewable energy if its production via water electrolysis and utilization in fuel cells are realized with high energy efficiency and non-precious electrocatalysts. In an unprecedented novel combination of structured electrodes with hydrogen converting enzymes from the uncultured and thus largely inaccessible microbial majority (>99%) we address this challenge. The geometrically defined electrodes with large specific surface area allow for low overpotentials and high energy efficiencies to be achieved. Enzymatic hydrogen evolution electrocatalysts are used as alternatives to noble metals. The enzymes are harnessed from the environmental microbial DNA (metagenomes) of hydrothermal vents exhibiting dynamic hydrogen and oxygen concentrations and are recovered via a recently developed novel activity-based screening tool. The screen enables us to target currently unrecognized hydrogenase enzymes from metagenomes via direct expression in a surrogate host microorganism. This circumvents the need for cultivation of the source organisms, the primary bottleneck when harnessing enzymes from microbes. One hydrogen converting metagenome-derived enzyme exhibited high activity and unusually high stability when dispersed on a TiO2-coated polyacrylonitrile fiber electrode. Our results highlight the tremendous potential of enzymes derived from uncultured microorganisms for applications in energy conversion and storage technologies.

AbstractCurrently, Sb2Se3 thin films receive considerable research interest as a solar cell absorber material. When completed into a device stack, the major bottleneck for further device improvement is the open‐circuit voltage, which is the focus of the work presented here. Polycrystalline thin‐film Sb2Se3 absorbers and solar cells are prepared in substrate configuration and the dominant recombination path is studied using photoluminescence spectroscopy and temperature‐dependent current–voltage characteristics. It is found that a post‐deposition annealing after the CdS buffer layer deposition can effectively remove interface recombination since the activation energy of the dominant recombination path becomes equal to the bandgap of the Sb2Se3 absorber. The increased activation energy is accompanied by an increased photoluminescence yield, that is, reduced non‐radiative recombination. Finished Sb2Se3 solar cell devices reach open‐circuit voltages as high as 485 mV. Contrarily, the short‐circuit current density of these devices is limiting the efficiency after the post‐deposition annealing. It is shown that atomic layer‐deposited intermediate buffer layers such as TiO2 or Sb2S3 can pave the way for overcoming this limitation.

The preparation of a flake‐like glass–ceramic anode material comprised of SiO2 and GeO2 for Li‐ion batteries (LIBs) is demonstrated. The precursor glass material is prepared via a traditional melt quenching technique. Flake‐like glass particles are obtained by compression in the liquid phase via ball milling. A subsequent heat treatment induces crystallization of GexSiyO6 domains inside the vitreous SiO2–GeO2 matrix. This novel glass‐ceramic material is applied as an anode material for LIBs and shows a stable reversible capacity of 520 mAh g−1 at 0.2 C combined with good capacity retention of 87% after 100 cycles. This cycling stability can be attributed to the synergistic effects of having nanocrystalline domains embedded in the glass matrix: The open glass network can withstand the volume change and stress caused by the lithium insertion during cycling, while the nanocrystals act as active sites for the electrochemical conversion and alloying reactions. The glass–ceramic anode material exhibits superior electrochemical properties compared to its pure glass counterparts.

Holistic performance characterization: not only one performance parameter, but short-term electrocatalytic proficiency in process relevant conditions combined with long-term stability.

Extremely thin absorber solar cells are built in which an Sb2S3 absorber coating is created by atomic layer deposition (ALD). The material is distributed homogeneously along the depth axis and is free of oxide. Under our conditions, an optimal thickness of 10 nm, Sb2S3, yields efficiencies of up to 2.6%.

We establish solution atomic layer deposition (sALD) for the controlled growth of pure Sb2Se3 thin films under mild conditions, namely, room temperature and atmospheric pressure. Upscaling this process yields Sb2Se3 thin films with high homogeneity over large-area (4 '') substrates. Annealing of the initially amorphous material leads to highly crystalline and smooth Sb2Se3 thin films. Removing the constraints of thermal stability and sufficient volatility in sALD compared to traditional gas-phase ALD opens up a broad choice of precursors and allows us to examine a wide range of Se2- precursors, of which some exhibit facile synthetic routes and allow us to tune their reactivity for optimal experimental ease of use. Moreover, we demonstrate that the solvent used in sALD represents an additional, attractive tool to influence and tailor the reactivity at the liquid-solid interface between the precursors and the surface. Je popsán řízený růst čistých tenkých vrstev Sb2Se3 za mírných podmínek, tj. při laboratorní teplotě a atmosférickém tlaku, metodou depozice atomárních vrstev v roztoku (sALD). Procesu poskytuje vysoce homogenní tenké filmy Sb2Se3 na velkoplošných (4'') substrátech. Použité rozpouštědlo v sALD se jeví jako účinný nástroj pro ovlivnění a přizpůsobení reaktivity na rozhraní kapalina-pevná látka mezi prekurzory a povrchem.