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

ZnO has emerged as a promising candidate for optoelectronic and microelectronic applications, whose development requires greater understanding and control of their electronic contacts. The rapid pace of ZnO research over the past decade has yielded considerable new information on the nature of ZnO interfaces with metals. Work on ZnO contacts over the past decade has now been carried out on high quality material, nearly free from complicating factors such as impurities, morphological and native point defects. Based on the high quality bulk and thin film crystals now available, ZnO exhibits a range of systematic interface electronic structure that can be understood at the atomic scale. Here we provide a comprehensive review of Schottky barrier and ohmic contacts including work extending over the past half century. For Schottky barriers, these results span the nature of ZnO surface charge transfer, the roles of surface cleaning, crystal quality, chemical interactions, and defect formation. For ohmic contacts...

ZnO Schottky barriers and Ohmic contacts

Summary: Carbazole-based oligomeric and polymeric materials have been studied for almost 25 years for their unique electrical, electrochemical and optical properties. Interestingly, carbazole units can be linked in two different ways leading to either poly(3,6-carbazole) or poly(2,7-carbazole) derivatives. While the former class seems to be very interesting for electrochemical and phosphorescence applications, the latter shows very promising optical properties in the visible range for light emitting diodes (LED). The major intrinsic difference between these two classes is the effective conjugation length: poly(2,7-carbazole) materials having the longer one, due to their poly(p-phenylene)-like structure. Using different synthetic strategies and substitution patterns, the physico-chemical properties of both classes can be fine-tuned, leading to high performance materials for a large number electronic applications.

Chemical structures for poly(3,6-carbazole) and poly(2,7-carbazole) and the materials used as the starting points for their respective syntheses.

Polycarbazoles: 25 Years of Progress

Ultraviolet (UV) photodetection has drawn a great deal of attention in recent years due to a wide range of civil and military applications. Because of its wide band gap, low cost, strong radiation hardness and high chemical stability, ZnO are regarded as one of the most promising candidates for UV photodetectors. Additionally, doping in ZnO with Mg elements can adjust the bandgap largely and make it feasible to prepare UV photodetectors with different cut-off wavelengths. ZnO-based photoconductors, Schottky photodiodes, metal–semiconductor–metal photodiodes and p–n junction photodetectors have been developed. In this work, it mainly focuses on the ZnO and ZnMgO films photodetectors. We analyze the performance of ZnO-based photodetectors, discussing recent achievements, and comparing the characteristics of the various photodetector structures developed to date.

https://www.mdpi.com/1424-8220/10/9/8604/pdf

ZnO-Based Ultraviolet Photodetectors

Ternary boron carbon nitride (BCN) semiconductors have been developed as emerging metal-free photocatalysts for visible-light reduction of CO2, but the achieved efficiency is still not satisfying. Herein, we report that the CO2 photoreduction performance of a bulk BCN semiconductor can be substantially improved by surface engineering with CdS nanoparticles. The CdS/BCN photocatalysts are characterized completely by diverse tests (e.g., XRD, FTIR, XPS, DRS, SEM, TEM, N2 sorption, PL, and transient photocurrent spectroscopy). Performance of the CdS/BCN heterostructures is evaluated by reductive CO2 conversion reactions with visible light under benign reaction conditions. Compared with bare BCN material, the optimized CdS/BCN photocatalyst exhibits a 10-fold-enhanced CO2 reduction activity and high stability, delivering a considerable CO production rate of 12.5 μmol h–1 (250 μmol h–1 g–1) with triethanolamine (TEOA) as the reducing agent. The reinforced photocatalytic CO2 reduction activity is mainly assigne...

Boron Carbon Nitride Semiconductors Decorated with CdS Nanoparticles for Photocatalytic Reduction of CO2

CuInS2/In2S3 thin film solar cell using spray pyrolysis technique having 9.5% efficiency

Role of precursor solution in controlling the opto-electronic properties of spray pyrolysed Cu2ZnSnS4 thin films

A Schottky ultraviolet photodiode using a (0001) ZnO single crystal grown by the hydrothermal growth method is reported. The photodiode consisted of a semitransparent Pt film for the Schottky electrode and an Al thin film for the Ohmic electrode. The photodiode had polarity dependences on current-voltage characteristics and on responsivity. In the case of the Schottky electrode on the zinc surface, the responsivity was 0.185A∕W at a wavelength of 365nm. On the other hand, the responsivity was 0.09A∕W for an oxygen surface. The results are attributed to the polarity dependences of surface chemical reactivity and the surface state density on ZnO surfaces.

Schottky ultraviolet photodiode using a ZnO hydrothermally grown single crystal substrate

In this paper we report for the first time the results of photoluminescence (PL) studies on thin films of a β-In2S3 compound semiconductor, grown using a chemical spray pyrolysis (CSP) technique. PL emission in the wavelength range 550–900 nm was recorded using a 488 nm line from a Ar+ laser as the excitation source. There were two PL bands, centred at 568 nm (band A) and 663 nm (band B). A shift in the PL peak energy and full width at half maximum of the former band due to a variation in temperature strongly suggested that the emission followed the Cartesian coordinate (CC) model of luminescence, while the latter was found to have arisen from transitions between a donor–acceptor pair. Band A was most dominant in the sulfur-deficient sample and hence associated with a sulfur vacancy, while band B was dominant in the indium-rich sample and hence linked with indium interstitials. The proposed energy level scheme allowed us to interpret the recombination processes in β-In2S3 thin films.

http://iopscience.iop.org/article/10.1088/0268-1242/20/12/003/pdf

Defect analysis of sprayed β-In2S3 thin films using photoluminescence studies

Preparation de polypyrrole dope a des concentrations variable de ClO 4 − par polymerisation electrochimique; augmentation de la conductivite avec la teneur en dopant et la densite de spin; la force thermoelectromotrice est caracteristique d'un semiconducteur p. et les courbes intensite/tension montrent un redressement remarquable, tout comme le contact polypyrrole/indium. Discussion des diagrammes de bande d'energie du polypyrrole et de l'heterojonction polypyrrole/n-Si

Yasube Kashiwaba

Papers

CuInS2/In2S3 thin film solar cell using spray pyrolysis technique having 9.5% efficiency

Role of precursor solution in controlling the opto-electronic properties of spray pyrolysed Cu2ZnSnS4 thin films

Schottky ultraviolet photodiode using a ZnO hydrothermally grown single crystal substrate

Defect analysis of sprayed β-In2S3 thin films using photoluminescence studies

Electronic properties of polypyrrole/n-Si heterojunctions and polypyrrole/metal contacts