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

Polycrystalline thin films of copper indium diselenide and its alloys with gallium and sulphur (CIGS) have proven to be suitable for use as absorbers in high-efficiency solar cells. Record efficiency devices of 20% power conversion efficiency have been produced by co-evaporation of the elements under high vacuum. However, non-vacuum methods for absorber deposition promise significantly lower capital expenditure and reduced materials costs, and have been used to produce devices with efficiencies of up to 14%. Such efficiencies are already high enough for commercial up-scaling to be considered and several companies are now trying to develop products based on non-vacuum deposited CIGS absorbers. This article will review the wide range of non-vacuum techniques that have been used to deposit CIGS thin films, highlighting the state of the art and efforts towards commercialization.

Non‐vacuum methods for formation of Cu(In, Ga)(Se, S)2 thin film photovoltaic absorbers

Cu2S−CuInS2 hybrid nanostructures as well as pure CuInS2 (CIS) nanocrystals were synthesized by methods of colloidal chemistry. The structure, the shape and the composition of these nanomaterials were investigated with transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX). By changing the reaction conditions, CuInS2 nanorods with different aspect ratio, dimeric nanorods as well as hexagonal discs and P-shaped particles could be synthesized. Under our reaction conditions, CIS nanoparticles crystallize in the hexagonal wurtzite structure, as confirmed by Rietveld analysis of the X-ray diffraction patterns. The formation of Cu2S−CuInS2 hybrid nanostructures turned out to be an essential intermediate step in the growth of CIS nanoparticles, the copper sulphide part of the hybrid material playing an important role in the shape control of the CIS nanocrystals. By a treatment of Cu2S−CuInS2 with 1,10-phenanthroline, Cu2S parts of the hybrid nanostructur...

Synthesis and shape control of CuInS(2) nanoparticles.

Efficient solar hydrogen production by photocatalytic water splitting: From fundamental study to pilot demonstration

Physical properties of ZnO thin films deposited by spray pyrolysis technique

Structural and optical properties of sprayed CuInS2 films

Composition and structure of CuInS2 films prepared by spray pyrolysis

Growth and recrystallization of CuInS2 films in spray pyrolytic process

Sprayed CuInS2 thin films for solar cells : The effect of solution composition and post-deposition treatments

ZnO thin films were deposited by spraying of zinc acetate solution onto heated glass substrates at 670 K. Highly textured in the (002) direction undoped ZnO films, exhibiting exciton emission bands in photoluminescence spectra at 8 K, were grown. The initial stages of the thin film growth and effect of doping with In, Ce and Eu were studied. A spraying time of 30 s leads to continuous crystalline films with well-shaped grains with narrow granulometric distribution and mean grain size close to 35 nm. Depositing times longer than 2 min lead to the solid phase sintering process. Wide granulometric distribution of the grains in the range of 50–400 nm was found for undoped films. It is shown that the size and orientation of crystallites in the film, the optical and electrical properties of the films are determined by the dopant concentration. As a result dense ZnO films with high optical transmittance were produced.

https://iopscience.iop.org/article/10.1238/Physica.Topical.079a00209/pdf

Olga Bijakina

Papers

Structural and optical properties of sprayed CuInS2 films

Composition and structure of CuInS2 films prepared by spray pyrolysis

Growth and recrystallization of CuInS2 films in spray pyrolytic process

Sprayed CuInS2 thin films for solar cells : The effect of solution composition and post-deposition treatments

Zinc oxide thin films by spray pyrolysis method