Among the armoury of photovoltaic materials, thin film heterojunction photovoltaics continue to be a promising candidate for solar energy conversion delivering a vast scope in terms of device design and fabrication. Their production does not require expensive semiconductor substrates and high temperature device processing, which allows reduced cost per unit area while maintaining reasonable efficiency. In this regard, superstrate CdTe/CdS solar cells are extensively investigated because of their suitable bandgap alignments, cost effective methods of production at large scales and stability against proton/electron irradiation. The conversion efficiencies in the range of 6–20% are achieved by structuring the device by varying the absorber/window layer thickness, junction activation/annealing steps, with more suitable front/back contacts, preparation techniques, doping with foreign ions, etc. This review focuses on fundamental and critical aspects like: (a) choice of CdS window layer and CdTe absorber layer; (b) drawbacks associated with the device including environmental problems, optical absorption losses and back contact barriers; (c) structural dynamics at CdS–CdTe interface; (d) influence of junction activation process by CdCl2 or HCF2Cl treatment; (e) interface and grain boundary passivation effects; (f) device degradation due to impurity diffusion and stress; (g) fabrication with suitable front and back contacts; (h) chemical processes occurring at various interfaces; (i) strategies and modifications developed to improve their efficiency. The complexity involved in understanding the multiple aspects of tuning the solar cell efficiency is reviewed in detail by considering the individual contribution from each component of the device. It is expected that this review article will enrich the materials aspects of CdTe/CdS devices for solar energy conversion and stimulate further innovative research interest on this intriguing topic.

Physics and chemistry of CdTe/CdS thin film heterojunction photovoltaic devices: fundamental and critical aspects

Recent status of chemical bath deposited metal chalcogenide and metal oxide thin films

Ce3+ and oxygen vacancy mediated tuning of structural and optical properties of CeO2 nanoparticles

Superhydrophobic cellulose-based products have immense potential in many industries where plastics and other polymers with hydrophobic properties are used. Superhydrophobic cellulose-based plastic is inherently biodegradable, renewable and non-toxic. Finding a suitable replacement of plastics is highly desired since plastics has become an environmental concern. Despite its inherent hydrophilicity, cellulose has unparalleled advantages as a substrate for the production of superhydrophobic materials which has been widely used in self-cleaning, self-healing, oil and water separation, electromagnetic interference shielding, etc. This review includes a comprehensive survey of the progress achieved so far in the production of super-hydrophobic materials based on cellulose and fiber networks. The method-ologies and applications of superhydrophobic-modified cellulose and fiber networks are emphasized. Overall, presented herein is targeting on summarizing some of the aspects that are critical to advance this evolving field of science which may provide new ideas for the developing and exploring of superhydrophobic and green-based materials.

Superhydrophobic modification of cellulose and cotton textiles: Methodologies and applications

Characterization of CdTe thin film—dependence of structural and optical properties on temperature and thickness

Influence of the thickness on structural, optical and electrical properties of chemical bath deposited CdS thin films

Recently there is an increased interest in developing magnetic semiconductors due to their promising applications in spintronics. The semiconductors can be made ferromagnetic by doping with transition-metal ions. In this paper, the results of our studies using x-ray diffraction (XRD) and IR and Raman spectroscopic techniques on the effect of Fe doping on the structural properties of SnO2 are presented. The XRD results showed that the doping affects the structure and the lattice constants decrease as doping concentration increases, reaches a minimum, and again increases. The doped samples are under compressive strain and the strain is maximum for the sample doped with 3% (at. %) Fe. The grain size of the nanoparticles decreases from 42nm in undoped SnO2 to 26nm in Sn0.90Fe0.10O2. It was observed that the preferred orientation is along the (101) direction and both texture coefficient and preferential orientation show a dependence on doping level. The Raman spectra showed clear evidences of the change in gra...

Structural modifications of SnO2 due to the incorporation of Fe into the lattice

XRD study of the grain growth in CdTe films annealed at different temperatures

The effect of annealing on the structure of CdTe films electro-deposited on metallic substrates

Cadmium telluride (CdTe) is one of the most investigated semiconductors for photovoltaic applications in the last four decades and is one of the most promising photovoltaic materials due to low-cost, high-efficiency, nearly optimum band gap (1.5 eV) for efficient photo conversion, high optical absorption coefficient (>104 cm−1) at band edge and the variety of deposition techniques available for its deposition as thin films. The close spaced sublimation (CSS) is one of the most promising methods to develop good quality CdTe films on large area substrates. There are various reports of the CdTe/CdS solar cells with efficiencies exceeding 16%, all prepared by CSS [1, 2]. In conventional solar cells, the CdTe is developed on the CdS window layer deposited on conducting glass substrates. But devices on glass substrates have the disadvantage of weight, inability to withstand high processing temperatures and are prone to damages. On the other hand devices on flexible metallic substrates can overcome all the above mentioned disadvantages of the glass based devices. Hence the development and characterization of CdTe on thin flexible metallic substrates are interesting. There are a number of reports regarding the characterization of CdTe thin films developed on CdS substrates by CSS, but practically no reports regarding the characterization of CdTe films developed on metallic substrates by CSS technique. We have deposited CdTe films on stainless steel by CSS at various source and substrate temperatures and the films were characterized using SEM and XRD. In this paper we are reporting the influence of the temperatures of substrate and source on the various structural parameters such as lattice parameter, grain size and stress. The investigations regarding the development of an interlayer between CdTe and the substrate are in progress and will be published in subsequent papers. The CSS system consists of a graphite reactor enclosed in a quartz tube. The tube was evacuated and

J. P. Enríquez

Papers

Influence of the thickness on structural, optical and electrical properties of chemical bath deposited CdS thin films

Structural modifications of SnO2 due to the incorporation of Fe into the lattice

XRD study of the grain growth in CdTe films annealed at different temperatures

The effect of annealing on the structure of CdTe films electro-deposited on metallic substrates

Structural characterization of CdTe thin films developed on metallic substrates by close spaced sublimation