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Gurgaon, India

Basu P.K.,Solar Energy Research Institute of Singapore | Basu P.K.,Munjal University | Li J.,Solar Energy Research Institute of Singapore | Shanmugam V.,Solar Energy Research Institute of Singapore | And 2 more authors.
RSC Advances | Year: 2016

Improvement in emitter and bulk regions of multicrystalline silicon (multi-Si) cells by phosphorus (P) gettering is a well-known technique. Earlier researchers exploited P gettering using a combination of deep emitter formation, complete emitter etching and re-diffusion, or, the use of sacrificial dielectric layers. In this work, our approach consists of heavy P diffusion in a tube diffusion furnace, followed by chemical etch-back of the P diffused layer. The novelty of our work is three-fold. Firstly, for the first time a low-cost, non-acidic emitter etch-back process - the 'SERIS etch' is applied on the tube-diffused emitter. Earlier the 'SERIS etch' was reported only for the inline-diffused cells. Secondly, a deep etch-back (change in sheet resistance by ∼40 Ω sq-1) is performed to get the advantage of P gettering on heavily diffused emitter without affecting its surface reflectance and doping uniformity. Thirdly, unlike previously reported works, our process does not required additional diffusion or dielectric deposition processes; hence it is cost-effective and industry competitive. For the screen-printed full-area aluminium back surface field multi-Si solar cells, an average cell efficiency gain of 0.5% (absolute) is observed for etched-back cells as compared to reference cells with as-diffused emitter (no etch-back). As both groups of cells are of same sheet resistance, the efficiency gain reflects the positive effect phosphorous diffusion gettering for the etch-back cells using our modified process. © The Royal Society of Chemistry 2016.

Shanmugam V.,Solar Energy Research Institute of Singapore | Shanmugam V.,National University of Singapore | Khanna A.,Solar Energy Research Institute of Singapore | Basu P.K.,Munjal University | And 4 more authors.
Solar Energy Materials and Solar Cells | Year: 2016

Metallisation of phosphorus-doped silicon (Si) surfaces using screen-printed silver (Ag) pastes is a well-established process and also a key process in the production of Si wafer solar cells. The metal-Si interface in a solar cell is a highly recombination-active region that impacts the device voltage. In this work, a facile test metallisation pattern with regions of varying front metal contact fractions is screen printed to create test cells on different phosphorus emitter doping profiles, all on commercially available multicrystalline Si wafers. On these and in conjunction with H-pattern cells and cells without front metallisation, intensity-dependent photoluminescence imaging is performed to extract both the metal-induced recombination saturation current densities and parameters related to wafer edge and peripheral recombination. It is observed that as the phosphorus emitter profile becomes lightly doped and shallower, the metallisation-induced recombination losses increase. The extracted metal recombination saturation current densities (J01-metal and J02-metal) on a 50. © 2015 Elsevier B.V. All rights reserved.

Mussada E.K.,Munjal University | Patowari P.K.,National Institute of Technology Silchar
Surface Engineering | Year: 2015

The present work focuses on characterisation of the deposited layer on aluminium substrate processed with electric discharge coating process. Different characterisation techniques such as scanning electron microscopy, energy dispersive X-ray and X-ray diffraction (XRD) have been employed to study the surface morphological changes, presence of materials and their phase transformations due to the formation and deposition of composite material layer on work surface. The grain size of the deposited particles has a significant effect on mechanical properties. Thus, an attempt has been made to calculate the grain size, dislocation density and microstrain of deposited material and its particles. The formation of tungsten carbides, namely, WC and W2C, is detected through XRD analysis. Clusters of globular particles in nanoscale are observed throughout the deposited layer. © 2015 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute.

Sharma A.,University of Delhi | Sridharbabu Y.,National Institute of Technology Kurukshetra | Quamara J.K.,Munjal University
Radiation Effects and Defects in Solids | Year: 2015

Thermally stimulated spontaneous currents in 75 MeV oxygen-ion-irradiated kapton-H polyimide samples sandwiched between similar (M-P-M) and dissimilar (M1-P-M2) electrodes in the temperature range of 20-250°C have been studied. Metals used as electrodes in the present investigations are having different work functions (Bi: 4.22, Al: 4.28, Cr: 4.37, Cu: 4.70 and Au: 5.1 eV). One maxima in the temperature region 30-60°C and other in the temperature region 100-120°C have been observed, termed as γ and β relaxations, respectively. γ-Relaxation is associated with the water absorption and β-relaxation is associated with the presence of dipoles in the material. The magnitude of the current depends on the type of electrode combinations used: either similar (M-P-M) or dissimilar (M1-P-M2) electrode systems. The value of current in M1-P-M2 combinations is more in comparison with M-P-M systems, as the internal potential difference developed in dissimilar electrodes is more as compared with the similar electrode system. The carbonyl groups present in the structure of kapton-H polyimide are the most affected group, due to the contact electrode system and ion irradiation. Aluminum atoms interact with imide carbonyl groups in kapton-H polyimide form carbonyl (>CO)-metal complex. As a result of ion irradiation, demerization of carbonyl groups and formation of some new polar-subpolar groups take place. The moisture in ion-irradiated samples promotes the current magnitude via helping in transport or conduction of charge carriers through polyimide. © 2015 Taylor & Francis.

Ahmed S.,Munjal University | Kaplan D.M.,Illinois Institute of Technology | Roberts T.J.,Muons, Inc. | Spentzouris L.K.,Illinois Institute of Technology
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2015

Particle-in-cell simulations involving the interaction of a muon beam (peak density 1018m-3 with Li plasma (ionized medium) of density 1016-1022m-3 have been performed. This study aimed to understand the effects of a plasma on an incoming beam in order to explore the dynamics during the process of ionization cooling. The computer code takes into account the self-consistent electromagnetic effects of a beam interacting with a plasma. This study shows that the beam can pass through plasmas with densities four orders of magnitude higher than the beam peak density. A low density (1016m-3) plasma is completely displaced by the beam; however, a strong wake is observed when the beam and plasma densities are comparable. Presence of an external magnetic field at the cooling channel helps to suppress the magnitude of the plasma wave. © 2015 Elsevier B.V. All rights reserved.

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