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P. K. Nair

Bio: P. K. Nair is an academic researcher from National Autonomous University of Mexico. The author has contributed to research in topics: Thin film & Chemical bath deposition. The author has an hindex of 17, co-authored 32 publications receiving 1138 citations.

Papers
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TL;DR: In this article, the basic concepts underlying the chemical bath deposition technique and recipes developed in our laboratory during the past ten years for the deposition of good-quality thin films of CdS, CdSe, ZnS, PbSe, SnS, Bi2S3, BiSe3, SbS3 Sb2S2, CuS, CuSe, etc.

345 citations

Journal ArticleDOI
TL;DR: In this article, the optical and electrical properties of two polymorphs of tin sulfide are compared in the context of light-generated current density in solar cells, and the authors conclude that the two SnS polymorphs when considered together as optical absorbers offer wider prospects for thin-film solar cells.
Abstract: The tin sulfide solar cell has acquired prominence in recent years. We present the characteristics of two polymorphs of SnS and their perspectives in thin-film solar cells. Thin-film SnS with cubic crystalline structure (SnS-CUB) was obtained via two chemical routes. This semiconductor is distinct from the more common SnS thin films of orthorhombic crystalline structure (SnS-ORT), also obtained by chemical routes. The SnS-CUB reported here with a lattice constant a of 11.587 A replaces the zinc blende structure previously reported for this material with a of 5.783 A. Thin films of SnS-CUB have an optical bandgap (Eg) of 1.66–1.72 eV and electrical conductivity (σ) of 10−6 Ω−1 cm−1. These characteristics distinguish them from SnS-ORT presented here with an Eg of 1.1 eV and σ typically higher by two orders of magnitude. We discuss the uncertainties that have prevailed in the assignment of crystalline structure for SnS-CUB and SnS-ORT. The optical and electrical properties of these two polymorphs of SnS are contrasted in the context of light-generated current density in solar cells. We conclude that the two SnS polymorphs when considered together as optical absorbers offer wider prospects for tin sulfide thin-film solar cells.

101 citations

Journal ArticleDOI
TL;DR: In this paper, a photo-accelerated chemical deposition (PACD) of PbS thin films is described, where an intensity distribution over the surface of a growing thin film produces a thickness variation (0.06-0.15 μm) of the film which, when viewed under daylight, yields a specularly reflective image.
Abstract: Metal sulphide thin film (MSTF) photography based on photo-accelerated chemical deposition (PACD) of PbS thin films is described. Here an intensity distribution over the surface of a growing PbS thin film produces a thickness variation (0.06–0.15 μm) of the film which, when viewed under daylight, yields a specularly reflective image. Under 800 W m−2 of solar radiation a bluish MSTF photographic image (0.15 μm film thickness) on a coppery-bronze background (0.08 μm) is obtained in the PACD of PbS at the end of 25 min deposition when a high-contrast photographic negative is used as the object. The best contrast of 0.46 in the PbS MSTF photography in the reflection mode is obtained under the above condition of exposure when the optical transmission in a photographic negative in the image area is ∽30% and that in the background is ∽1%. The contrast available in the transmission mode in the MSTF photographic image is considerably less: ∽0.28 (maximum) for optical transmission of 1% and 100% in the background and image areas of the photographic negative respectively.

94 citations

Journal ArticleDOI
TL;DR: In this article, a solar cell with stainless steel/snS/CdS/ZnO/ZNO:Al was constructed, and the authors reported conversion efficiency of 1.28%, open-circuit voltage (Voc) of 0.470
Abstract: In a solar cell: stainless steel/SnS/CdS/ZnO/ZnO:Al, we report conversion efficiency of 1.28%, open-circuit voltage (Voc) of 0.470 V, and short-circuit current density (Jsc) of 6.2 mA cm−2, measured on cells of area 1 cm2 under standard conditions. The thin film of SnS absorber of 550 nm in thickness used in this cell was deposited from a chemical bath. Average crystalline diameter of the material is 24 nm, and its X-ray diffraction pattern fits a cubic unit cell with cube edge of 1.159 nm. The optical band gap of the material is 1.74 eV and its electrical conductivity is 10−6 Ω−1 cm−1. The mobility-lifetime product of the film was determined as 2 × 10−7 cm2 V−1 from photoconductivity measurement. To build the solar cell, a CdS thin film of 50 nm in thickness was deposited from a chemical bath on the SnS thin film prepared on the stainless steel substrate. Subsequently, a ZnO film of 180 nm and ZnO:Al film of 450 nm in thickness were deposited on this CdS defining a solar cell area of 1 cm2. This solar cell is stable under concentrated sunlight of 2–16 suns, attaining Voc of 0.6 V and Jsc of 35 mA cm−2 under 16 suns.

86 citations

Journal ArticleDOI
TL;DR: In this article, a method for obtaining thin films of polycrystalline antimony selenide via chemical bath deposition followed by heating the thin films at 573 K in selenium vapor was reported.

75 citations


Cited by
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Journal ArticleDOI
TL;DR: This review aims to comprehensively summarize the state-of-the-art strategies for the realization of high-performance thermoelectric materials and devices by establishing the links between synthesis, structural characteristics, properties, underlying chemistry and physics.
Abstract: The long-standing popularity of thermoelectric materials has contributed to the creation of various thermoelectric devices and stimulated the development of strategies to improve their thermoelectric performance. In this review, we aim to comprehensively summarize the state-of-the-art strategies for the realization of high-performance thermoelectric materials and devices by establishing the links between synthesis, structural characteristics, properties, underlying chemistry and physics, including structural design (point defects, dislocations, interfaces, inclusions, and pores), multidimensional design (quantum dots/wires, nanoparticles, nanowires, nano- or microbelts, few-layered nanosheets, nano- or microplates, thin films, single crystals, and polycrystalline bulks), and advanced device design (thermoelectric modules, miniature generators and coolers, and flexible thermoelectric generators). The outline of each strategy starts with a concise presentation of their fundamentals and carefully selected examples. In the end, we point out the controversies, challenges, and outlooks toward the future development of thermoelectric materials and devices. Overall, this review will serve to help materials scientists, chemists, and physicists, particularly students and young researchers, in selecting suitable strategies for the improvement of thermoelectrics and potentially other relevant energy conversion technologies.

951 citations

Journal ArticleDOI
TL;DR: In this article, the authors have described in detail, chemical bath deposition method of metal chalcogenide thin films, it is capable of yielding good quality thin films and their preparative parameters, structural, optical, electrical properties etc.

733 citations

Journal ArticleDOI
TL;DR: In this article, the successive ionic layer adsorption and reaction (SILAR) method has emerged as one of the solution methods to deposit a variety of compound materials in thin film form.
Abstract: During last three decades, successive ionic layer adsorption and reaction (SILAR) method, has emerged as one of the solution methods to deposit a variety of compound materials in thin film form. The SILAR method is inexpensive, simple and convenient for large area deposition. A variety of substrates such as insulators, semiconductors, metals and temperature sensitive substrates (like polyester) can be used since the deposition is carried out at or near to room temperature. As a low temperature process, it also avoids oxidation and corrosion of the substrate. The prime requisite for obtaining good quality thin film is the optimization of preparative provisos viz. concentration of the precursors, nature of complexing agent, pH of the precursor solutions and adsorption, reaction and rinsing time durations etc. In the present review article, we have described in detail, successive ionic layer adsorption and reaction (SILAR) method of metal chalcogenide thin films. An extensive survey of thin film materials prepared during past years is made to demonstrate the versatility of SILAR method. Their preparative parameters and structural, optical, electrical properties etc are described. Theoretical background necessary for the SILAR method is also discussed.

577 citations

Journal ArticleDOI
TL;DR: In this article, the authors showed that elemental Se at nano size (Nano-Se) possessed equal efficacy in increasing the activities of glutathione peroxidase, thioredoxin reductase, and glutathion S-transferase, but had much lower toxicity as indicated by median lethal dose, acute liver injury, survival rate, and short-term toxicity.

454 citations

Journal ArticleDOI
TL;DR: In this paper, a resonant optical filter design based on a modified, asymmetric metal was proposed to overcome the difficulties associated with the nanofabrication using a lithography-free approach.
Abstract: Nanostructured photonic materials enable control and manipulation of light at subwavelength scales and exhibit unique optical functionalities. In particular, plasmonic materials and metamaterials have been widely utilized to achieve spectral transmission, reflection, and absorption filters based on localized or delocalized resonances arising from the interaction of photons with nanostructured materials. Realization of visible-frequency, high-performance, large-area, optical filters based on nanoplasmonic materials is rather challenging due to nanofabrication related problems (cost, fabrication imperfection, surface roughness) and optical losses of metals. Here, we propose and demonstrate large-area perfect absorbers and transmission filters that overcome difficulties associated with the nanofabrication using a lithography-free approach. We also utilize and benefit from the optical losses in metals in our optical filter designs. Our resonant optical filter design is based on a modified, asymmetric metal–in...

398 citations