Nini Rose Mathews

Bio: Nini Rose Mathews is an academic researcher from National Autonomous University of Mexico. The author has contributed to research in topics: Thin film & Band gap. The author has an hindex of 24, co-authored 74 publications receiving 1828 citations. Previous affiliations of Nini Rose Mathews include Kuwait University & University of Texas at Dallas.

Tin Sulfide Thin Films by Pulse Electrodeposition: Structural, Morphological, and Optical Properties

Abstract: Tin sulfide thin films, typically 350 nm thick, were deposited on SnO 2 :F-coated transparent conductive oxide glass substrates by pulse electrodeposition. The applied potentials were V on = -0.9 V and V off = 0.1 V vs saturated calomel electrode with pulse on/off durations of 10 s. The films crystallized in the orthorhombic structure corresponding to SnS (herzenbergite), with grain size varying in the range from a few nanometers to more than 100 nm. X-ray diffraction analysis shows an average size of 12 nm; however, scanning electron microscopy and transmission electron microscopy images show the presence of large crystallites with well-developed facets along with agglomerations of smaller crystallites. Estimation of the bandgap from the optical spectra of these films showed absorption due to direct transition occurring at 1.3 eV. Elemental compositions of these SnS samples determined using energy dispersive X-ray spectroscopy were 51.4 and 48.5%, respectively, for Sn and S. Raman spectra suggested the presence of traces of Sn 2 S 3 and SnS 2 . The surface analysis by X-ray photoelectron spectroscopy showed the presence of traces of metallic Sn. The films are photosensitive with a dark resistivity 10 6 Ω cm.

Thin-film solar cells: an overview

Abstract: Thin film solar cells (TFSC) are a promising approach for terrestrial and space photovoltaics and offer a wide variety of choices in terms of the device design and fabrication. A variety of substrates (flexible or rigid, metal or insulator) can be used for deposition of different layers (contact, buffer, absorber, reflector, etc.) using different techniques (PVD, CVD, ECD, plasma-based, hybrid, etc.). Such versatility allows tailoring and engineering of the layers in order to improve device performance. For large-area devices required for realistic applications, thin-film device fabrication becomes complex and requires proper control over the entire process sequence. Proper understanding of thin-film deposition processes can help in achieving high-efficiency devices over large areas, as has been demonstrated commercially for different cells. Research and development in new, exotic and simple materials and devices, and innovative, but simple manufacturing processes need to be pursued in a focussed manner. Which cell(s) and which technologies will ultimately succeed commercially continue to be anybody's guess, but it would surely be determined by the simplicity of manufacturability and the cost per reliable watt. Cheap and moderately efficient TFSC are expected to receive a due commercial place under the sun.

Accelerating materials development for photoelectrochemical hydrogen production: Standards for methods, definitions, and reporting protocols

Abstract: Photoelectrochemical (PEC) water splitting for hydrogen production is a promising technology that uses sunlight and water to produce renewable hydrogen with oxygen as a by-product. In the expanding field of PEC hydrogen production, the use of standardized screening methods and reporting has emerged as a necessity. This article is intended to provide guidance on key practices in characterization of PEC materials and proper reporting of efficiencies. Presented here are the definitions of various efficiency values that pertain to PEC, with an emphasis on the importance of solar-to-hydrogen efficiency, as well as a flow chart with standard procedures for PEC characterization techniques for planar photoelectrode materials (i.e., not suspensions of particles) with a focus on single band gap absorbers. These guidelines serve as a foundation and prelude to a much more complete and in-depth discussion of PEC techniques and procedures presented elsewhere.

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

Abstract: 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.