In recent years, nanocrystals of metal sulfide materials have attracted scientific research interest for renewable energy applications due to the abundant choice of materials with easily tunable electronic, optical, physical and chemical properties. Metal sulfides are semiconducting compounds where sulfur is an anion associated with a metal cation; and the metal ions may be in mono-, bi- or multi-form. The diverse range of available metal sulfide materials offers a unique platform to construct a large number of potential materials that demonstrate exotic chemical, physical and electronic phenomena and novel functional properties and applications. To fully exploit the potential of these fascinating materials, scalable methods for the preparation of low-cost metal sulfides, heterostructures, and hybrids of high quality must be developed. This comprehensive review indicates approaches for the controlled fabrication of metal sulfides and subsequently delivers an overview of recent progress in tuning the chemical, physical, optical and nano- and micro-structural properties of metal sulfide nanocrystals using a range of material fabrication methods. For hydrogen energy production, three major approaches are discussed in detail: electrocatalytic hydrogen generation, powder photocatalytic hydrogen generation and photoelectrochemical water splitting. A variety of strategies such as structural tuning, composition control, doping, hybrid structures, heterostructures, defect control, temperature effects and porosity effects on metal sulfide nanocrystals are discussed and how they are exploited to enhance performance and develop future energy materials. From this literature survey, energy conversion currently relies on a limited range of metal sulfides and their composites, and several metal sulfides are immature in terms of their dissolution, photocorrosion and long-term durability in electrolytes during water splitting. Future research directions for innovative metal sulfides should be closely allied to energy and environmental issues, along with their advanced characterization, and developing new classes of metal sulfide materials with well-defined fabrication methods.

Recent advances in metal sulfides: from controlled fabrication to electrocatalytic, photocatalytic and photoelectrochemical water splitting and beyond

This review captures the synthesis, assembly, properties, and applications of copper chalcogenide NCs, which have achieved significant research interest in the last decade due to their compositional and structural versatility. The outstanding functional properties of these materials stems from the relationship between their band structure and defect concentration, including charge carrier concentration and electronic conductivity character, which consequently affects their optoelectronic, optical, and plasmonic properties. This, combined with several metastable crystal phases and stoichiometries and the low energy of formation of defects, makes the reproducible synthesis of these materials, with tunable parameters, remarkable. Further to this, the review captures the progress of the hierarchical assembly of these NCs, which bridges the link between their discrete and collective properties. Their ubiquitous application set has cross-cut energy conversion (photovoltaics, photocatalysis, thermoelectrics), en...

Compound Copper Chalcogenide Nanocrystals

Perspectives on oblique angle deposition of thin films: From fundamentals to devices

https://pubs.rsc.org/en/content/articlepdf/2017/cc/c6cc06475b

Beyond methylammonium lead iodide: prospects for the emergent field of ns2 containing solar absorbers

Three-Dimensional Titanium Dioxide Nanomaterials

The effect of several deposition parameters on the uniformity of copper electrodeposition through the alumina barrier layer into porous aluminum oxide templates grown in sulfuric or oxalic acid was systematically investigated. A fractional factorial design of experiment was conducted to find suitable deposition conditions among the variables: frequency, voltage, pulsed or continuous deposition, electrolyte concentration, and barrier layer thinning voltage. Continuous ac sine wave deposition conditions yielded excellent uniformity of pore-filling but damaged the porous aluminum oxide templates when deposition was continued to grow bulk copper on the surface. Pulsed electrodeposition yielded comparable uniformity of pore-filling and no damage to the porous aluminum oxide templates, even when bulk copper was deposited on them. Further optimization of pulsed deposition conditions was accomplished by comparing square and sine waveforms and pulse polarity. Pulsed square waveforms produced better pore-filling than pulsed sine waveforms. For sine wave depositions, the oxidative/reductive pulse polarity was more efficient than the commonly used reductive/oxidative pulse polarity. For square wave depositions into sulfuric acid grown pores, the reductive/oxidative pulse polarity produces more uniform pore-filling, likely as a result of enhanced resonant tunneling through the barrier layer and reoxidation of copper in faster filling pores.

Effect of ac electrodeposition conditions on the growth of high aspect ratio copper nanowires in porous aluminum oxide templates.

We have synthesized Cu3BiS3 thin films on fused silica substrates in a one-step process by reactive sputter deposition of Cu−S and Bi on hot substrates. This one-step process produces films that are crystalline, phase-pure, dense, smooth, and continuous. As-deposited films have a direct forbidden band gap of 1.4 eV, an optical absorption coefficient of 1 × 105 cm-1 at 1.9 eV, p-type conductivity, and an electrical resistivity of 84 Ω·cm. Postdeposition annealing in an H2S atmosphere increases crystallite size and reduces electrical resistivity of films to 9.6 Ω cm.

One-Step Synthesis and Optical and Electrical Properties of Thin Film Cu3BiS3 for Use as a Solar Absorber in Photovoltaic Devices

The synthesis of Cu3BiS3 thin films on fused silica substrates by heating Cu−Bi metal precursor films and Cu−S−Bi metal sulfide precursor films in a H2S atmosphere has been investigated. We have systematically evaluated the effect of precursor composition and structure, heating temperature, heating profile, and gas composition and pressure. Phase-pure Cu3BiS3 films 250−1000 nm thick were formed, with the morphology of the resulting films being highly dependent on the composition, structure, and heating profile of the precursor films. It was found that precursor composition determines the reaction pathway, and that the reaction pathway is the dominant factor in controlling the morphology of the Cu3BiS3 thin film. This precursor/pathway/morphology relationship results in Cu3BiS3 thin films that are discontinuous or contain hollow pockets between the film and substrate, regardless of the processing conditions employed. The electrical resistivity of these Cu3BiS3 films ranged from 3−200 Ω cm.

Synthesis of Cu3BiS3 Thin Films by Heating Metal and Metal Sulfide Precursor Films under Hydrogen Sulfide

Effect of TiO2 film porosity and thermal processing on TiO2–P3HT hybrid materials and photovoltaic device performance

A photovoltaic device, comprises a first electrode, an electron donor layer in electrical contact with the first electrode, an electron acceptor layer in contact with the electron donor layer across an interface having a shape defined by a columnar structure grown by oblique angle deposition, and a second electrode in electrical contact with the electron acceptor layer.

Nathan J. Gerein

Papers

Effect of ac electrodeposition conditions on the growth of high aspect ratio copper nanowires in porous aluminum oxide templates.

One-Step Synthesis and Optical and Electrical Properties of Thin Film Cu3BiS3 for Use as a Solar Absorber in Photovoltaic Devices

Synthesis of Cu3BiS3 Thin Films by Heating Metal and Metal Sulfide Precursor Films under Hydrogen Sulfide

Effect of TiO2 film porosity and thermal processing on TiO2–P3HT hybrid materials and photovoltaic device performance

Photovoltaic device based on conformal coating of columnar structures