Efficient direct solar-to-hydrogen conversion by in situ interface transformation of a tandem structure

Photosynthesis is nature’s route to convert intermittent solar irradiation into storable energy, while its use for an industrial energy supply is impaired by low efficiency. Artificial photosynthesis provides a promising alternative for efficient robust carbon-neutral renewable energy generation. The approach of direct hydrogen generation by photoelectrochemical water splitting utilizes customized tandem absorber structures to mimic the Z-scheme of natural photosynthesis. Here a combined chemical surface transformation of a tandem structure and catalyst deposition at ambient temperature yields photocurrents approaching the theoretical limit of the absorber and results in a solar-to-hydrogen efficiency of 14%. The potentiostatically assisted photoelectrode efficiency is 17%. Present benchmarks for integrated systems are clearly exceeded. Details of the in situ interface transformation, the electronic improvement and chemical passivation are presented. The surface functionalization procedure is widely applicable and can be precisely controlled, allowing further developments of high-efficiency robust hydrogen generators

Monolithic Photoelectrochemical Device for 19% Direct Water Splitting

Efficient unassisted solar water splitting, a pathway to storable renewable energy in the form of chemical bonds, requires optimization of a photoelectrochemical device based on photovoltaic tandem heterojunctions. We report a monolithic photocathode device architecture that exhibits significantly reduced surface reflectivity, minimizing parasitic light absorption and reflection losses. A tailored multifunctional crystalline titania interphase layer acts as a corrosion protection layer, with favorable band alignment between the semiconductor conduction band and the energy level for water reduction, facilitating electron transport at the cathode–electrolyte interface. It also provides a favorable substrate for adhesion of high-activity Rh catalyst nanoparticles. Under simulated AM 1.5G irradiation, solar-to-hydrogen efficiencies of 19.3 and 18.5% are obtained in acidic and neutral electrolytes, respectively. The system reaches a value of 0.85 of the theoretical limit for photoelectrochemical water splitting for the energy gap combination employed in the tandem-junction photoelectrode structure

Bioinformatic analyses of integral membrane transport proteins encoded within the genome of the planctomycetes species, Rhodopirellula baltica

Rhodopirellula baltica (R. baltica) is a Planctomycete, known to have intracellular membranes. Because of its unusual cell structure and ecological significance, we have conducted comprehensive analyses of its transmembrane transport proteins. The complete proteome of R. baltica was screened against the Transporter Classification Database (TCDB) to identify recognizable integral membrane transport proteins. 342 proteins were identified with a high degree of confidence, and these fell into several different classes. R. baltica encodes in its genome channels (12%), secondary carriers (33%), and primary active transport proteins (41%) in addition to classes represented in smaller numbers. Relative to most non-marine bacteria, R. baltica possesses a larger number of sodium-dependent symporters but fewer proton-dependent symporters, and it has dimethylsulfoxide (DMSO) and trimethyl-amine-oxide (TMAO) reductases, consistent with its Na-rich marine environment. R. baltica also possesses a Na-translocating NADH:quinone dehydrogenase (Na-NDH), a Na efflux decarboxylase, two Na-exporting ABC pumps, two Na-translocating F-type ATPases, two Na:H antiporters and two K:H antiporters. Flagellar motility probably depends on the sodium electrochemical gradient. Surprisingly, R. baltica also has a complete set of H-translocating electron transport complexes similar to those present in α-proteobacteria and eukaryotic mitochondria. The transport proteins identified proved to be typical of the bacterial domain with little or no indication of the presence of eukaryotic-type transporters. However, novel functionally uncharacterized multispanning membrane proteins were identified, some of which are found only in Rhodopirellula species, but others of which are widely distributed in bacteria. The analyses lead to predictions regarding the physiology, ecology and evolution of R. baltica

Metal-Organic-Vapor-Phase-Epitaxy of high-efficiency III-V solar cells

Die Arbeit beschäftigt sich mit der Epitaxie von III-V Solarzellen aus GaAs, GaInAs, GaInP, GaInP/GaAs, und GaInP/GaInAs. Es werden die verschiedenen Schritte der Herstellung und Optimierung der Struktur von der Epitaxie bis hin zur Kontakttechnologie und Meßtechnik der fertigen Solarzelle behandelt. Die Strukturen wurden mit Hilfe eines in der Halbleiterindustrie eingesetzten Reaktors zur Metallorganischen- Gasphasenepitaxie hergestellt. Die Arbeit beschäftigt sich mit der Optimierung der Abscheidebedingungen zum Wachstum von Schichten aus GaAs, AlGaInP, AlGaAs und GaInAs auf GaAs und Ge Substrat. Herausragend sind die Ergebnisse zu Solarzellen auf der Basis von GaInAs, fehlangepaßt gewachsen auf GaAs Substrat. Erstmals wurden Tandemsolarzellen aus GaInP auf GaInAs realisiert und ein Rekordwirkungsggrad von bis zu 31.3 bei einer Konzentration von 300 Sonnen erreicht

Mehrfachsolarzelle mit rückseitiger Germanium-Teilzelle und deren Verwendung

Die vorliegende Erfindung betrifft Mehrfachsolarzellen mit mindestens vier pn-Übergängen mit einer lichtabgewandten rückseitigen Germanium-Teilzelle und mindestens drei oberhalb der Germanium-Teilzelle angeordneten Teilzellen aus III-V Verbindungshalbleitern, wobei die Mehrfachsolarzellen mindestens eine metamorphe Pufferschicht und mindestens eine Waferbond-Verbindung aufweisen und alle Schichten, die oberhalb der Germanium-Teilzelle angeordnet sind, jeweils eine lichtabsorbierende Emitter- und/oder Basisschicht enthalten, die mindestens 20 % Indium, bezogen auf die Summe aller Atome der Gruppe III, enthalten. Weiterhin betrifft die vorliegende Erfindung die Verwendung dieser Mehrfachsolarzellen im Weltraum

Optimization of GaAs solar cell performance and growth efficiency at MOVPE growth rates of 100 μm/h

III-V devices outperform all other solar cells in terms of efficiency. However, the manufacturing of these cells is expensive and prevents their use in a number of applications, which would benefit from the high efficiency. A major contribution to the cost is the metal-organic vapor phase epitaxy process for the III-V compounds. Increasing growth rates and, hence, machine throughput, as well as the growth efficiency, are important steps toward reducing the cost of III-V solar cells. We demonstrate the growth of GaAs solar cells at extremely high growth rates of 100 μm/h and achieve a VOC of 1.028 V, a base diffusion length of 6.5 μm, and an efficiency of 23.6% under AM1.5g conditions. Furthermore, we show reactor adjustments leading to growth rates up to 140 μm/h and reach conditions where more than half of the Ga from the precursor is incorporated into the solar cell layers. The results are encouraging and demonstrate a pathway toward lower cost III-V solar cell manufacturing

Manufacture of Multijunction Solar Cell Devices

The present invention relates to a method for manufacturing a multijunction solar cell device comprising the steps of providing a first substrate; providing a second substrate having a lower surface and an upper surface; forming at least one first solar cell layer on the first substrate to obtain a first wafer structure; forming at least one second solar cell layer on the upper surface of the second substrate to obtain a second wafer structure; bonding the first wafer structure to the second wafer structure wherein the at least one first solar cell layer is bonded to the lower surface of the second substrate and removing the first substrate

Mehrfachsolarzelle und deren Verwendung

Die Erfindung betrifft eine Mehrfachsolarzelle mit mindestens drei pn-Übergängen sowie einer mittleren Teilzelle, die zwischen der Emitter-Schicht und der Basisschicht mindestens eine weitere Schicht mit erhöhter Bandlückenenergie aufweist. Diese Mehrfachsolarzelle kann sowohl im Weltraum, als auch in terrestrischen Konzentratorsystemen verwendet werden