V. Damodara Das

Bio: V. Damodara Das is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Thin film & Electrical resistivity and conductivity. The author has an hindex of 20, co-authored 89 publications receiving 1145 citations.

Fabrication and characterization of photoelectrochemical (PEC) solar cells based on 0.1% indium-doped CdSe0.7Te0.3 thin-film electrode

Abstract: Photoelectrochemical (PEC) solar cells have been fabricated using an aqueous poly-iodide solution electrolyte and thin-film photoelectrodes in the form of vacuum flash-evaporated thin films of 0.1% indium-doped CdSe0.7Te0.3 semiconducting photovoltaic alloy as one of the electrodes. For this, thin films of the CdSe0.7Te0.3 alloy were prepared by vacuum flash-evaporation of the bulk alloy ingot powder on thoroughly cleaned glass substrates held at room temperature in a vacuum of 6.5×10−5 mbar. The counter electrode was graphite. Different thickness films were deposited in separate depositions to study the effect of thickness on the solar cell efficiency. Also, some of the films were given different surface and heat treatments, viz. etching, photoetching and annealing, to study the effect of annealing and surface treatments on the efficiency of the solar cells formed using these films as photoelectrodes. It was found that the PEC solar cells formed exhibited an increase in efficiency of the conversion of light into electrical energy when the thin-film electrodes were annealed, etched or/and photoetched. The increase in efficiency was between 80 and 100%. An approximate six-fold increase in the thickness of the thin-film electrodes also led to an increase in efficiency of up to 80%. The results of the investigations are discussed and explained.

Growth of Thermoelectric Bia5Sb1~ Alloy Thin Films and their Characterization by XRD, TEM & RBS

Abstract: Bismuth and antimony are semimetals. The Bi,j.,,Sb, alloys (0.04

A review on thermoelectric renewable energy: Principle parameters that affect their performance

Abstract: Developing thermoelectric materials with superior performance means tailoring interrelated thermoelectric physical parameters – electrical conductivities, Seebeck coefficients, and thermal conductivities – for a crystalline system. High electrical conductivity, low thermal conductivity, and a high Seebeck coefficient are desirable for thermoelectric materials. Therefore, knowledge of the relation between electrical conductivity and thermal conductivity is essential to improve thermoelectric properties. In general, research in recent years has focused on developing thermoelectric structures and materials of high efficiency. The importance of this parameter is universally recognized; it is an established, ubiquitous, routinely used tool for material, device, equipment and process characterization both in the thermoelectric industry and in research. In this paper, basic knowledge of thermoelectric materials and an overview of parameters that affect the figure of merit ZT are provided. The prospects for the optimization of thermoelectric materials and their applications are also discussed.

Vortex formation in neutron-irradiated superfluid 3He as an analogue of cosmological defect formation

Abstract: TOPOLOGICAL defects formed during a rapid symmetry-breaking phase transition in the early Universe1,2 could be responsible for seeding large-scale structure, for the anisotropy of the microwave background radiation, and for the predominance of matter over antimatter3,4. The theory describing this cosmological phase transition is formally analogous to that describing the transition to the superfluid state in liquid 3He, so that in principle the process of cosmological defect formation can be modelled in the laboratory. Here we report the results of an experiment in which the 'primordial fireball' is mimicked using a neutron-induced nuclear reaction (n + 3He → p + 3He + 0.76 MeV) to heat small regions of superfluid 3He above the superfluid transition temperature. These bubbles of normal liquid cool extremely rapidly, and we find that their transition back to the superfluid state is accompanied by the formation of a random network of vortices (the superfluid analogue of cosmic strings). We monitor the evolution of this defect state by rotating the superfluid sample, allowing vortices to escape from the network and thus be probed individually. Our results provide clear confirmation of the idea that topological defects form at a rapid second-order phase transition, and give quantitative support to the Kibble–Zurek mechanism5,6 of cosmological defect formation.

Investigation of the optical and electronic properties of Ge2Sb2Te5 phase change material in its amorphous, cubic, and hexagonal phases

Abstract: Ge–Sb–Te alloys are widely used for data recording based on the rapid and reversible amorphous-to-crystalline phase transformation that is accompanied by increases in the optical reflectivity and the electrical conductivity. However, uncertainties about the optical band gaps and electronic transport properties of these phases have persisted because of inappropriate interpretation of reported data and the lack of definitive analytical studies. In this paper we characterize the most widely used composition, Ge2Sb2Te5, in its amorphous, face-centered-cubic, and hexagonal phases, and explain the origins of inconsistent or unphysical results in previous reports. The optical absorption in all of these phases follows the relationship αhν∝(hν−Egopt)2, which corresponds to the optical transitions in most amorphous semiconductors as proposed by Tauc, Grigorovici, and Vancu [Tauc et al., Phys. Status Solidi 15, 627 (1966)], and to those in indirect-gap crystalline semiconductors. The optical band gaps of the amorpho...

Functional inks and printing of two-dimensional materials.

Abstract: Graphene and related two-dimensional materials provide an ideal platform for next generation disruptive technologies and applications. Exploiting these solution-processed two-dimensional materials in printing can accelerate this development by allowing additive patterning on both rigid and conformable substrates for flexible device design and large-scale, high-speed, cost-effective manufacturing. In this review, we summarise the current progress on ink formulation of two-dimensional materials and the printable applications enabled by them. We also present our perspectives on their research and technological future prospects.

Effect of magnetic dipolar interactions on nanoparticle heating efficiency: Implications for cancer hyperthermia

Abstract: Nanostructured magnetic systems have many applications, including potential use in cancer therapy deriving from their ability to heat in alternating magnetic fields. In this work we explore the influence of particle chain formation on the normalized heating properties, or specific loss power (SLP) of both low- (spherical) and high- (parallelepiped) anisotropy ferrite-based magnetic fluids. Analysis of ferromagnetic resonance (FMR) data shows that high particle concentrations correlate with increasing chain length producing decreasing SLP. Monte Carlo simulations corroborate the FMR results. We propose a theoretical model describing dipole interactions valid for the linear response regime to explain the observed trends. This model predicts optimum particle sizes for hyperthermia to about 30% smaller than those previously predicted, depending on the nanoparticle parameters and chain size. Also, optimum chain lengths depended on nanoparticle surface-to-surface distance. Our results might have important implications to cancer treatment and could motivate new strategies to optimize magnetic hyperthermia.