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3. Programmable Charge Trap for Junction-less selective extraction of holes in Solar Cells

Author

Bhatia, Swasti, Antony, Aldrin, and Nair, Pradeep R.

Subjects
Physics - Applied Physics, Condensed Matter - Other Condensed Matter
Abstract

Selective extraction of photo-generated carriers is a fundamental challenge in solar cells which is usually achieved through junctions with the associated doping as well as band offset differences. In this context, here we propose a new paradigm for selective extraction for majority carriers through novel usage of the programmable charge trap which comprises of Oxide-Nitride-Oxide (ONO) stack and has the primary function of holding electrically injected charge. Through detailed numerical simulations, here we show that such a charge trap with an additional metal contact can (i) compensate for efficiency loss due to sub-optimal passivation and sub-optimal hole selectivity in homojunction as well as transition metal oxide-based heterojunction solar cells and (ii) can also function as a standalone hole selection scheme. The proposed scheme, with its easy integration and the capability of programmable compensation of performance loss, is of interest to the photovoltaic community.

Published
2022

7. Material and Process Tolerant High Efficiency Solar Cells with Dynamic Recovery of Performance

Author

Chatterji, Nithin, Bhatia, Swasti, Kumar, Anil, Antony, Aldrin, and Nair, Pradeep R.

Subjects
Physics - Applied Physics
Abstract

Low cost, highly efficient, and stable solar cells demand low temperature processing, less stringent criteria on materials, and possibility of dynamic recovery from long term degradation: a combination of features unachievable from the perspectives of current cSi technology. To this end, here we propose a novel solar cell architecture with an additional control gate. Our simulation results indicate that the proposed device can achieve excellent efficiency even if the back-surface passivation is sub-optimal; thus allowing exploration of a wide variety of materials and low temperature fabrication processes. Importantly, such solar cells can dynamically offset efficiency loss due to elevated temperature and interface degradation associated with long term field operation and hence could be of broad interest to the PV community., Comment: 4 pages, 4 figures, Updated version accepted for publication in IEEE Transactions on Electron Devices

Published
2021
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17. Temperature coefficient of Silicon based carrier selective solar cells

Author

Chatterji, Nithin, Antony, Aldrin, and Nair, Pradeep R.

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science
Abstract

Carrier Selective (CS) Silicon solar cells are increasingly explored as a low cost alternative to PN junction Silicon solar cells. While the recent trends on power conversion efficiency are encouraging, the temperature coefficient and hence the power output under elevated temperatures are not well explored for such solar cells. Here, we address this issue through detailed numerical simulations to explore the influence of interface and material parameters on the temperature coefficient. Our results indicate that irrespective of the interface quality, the temperature coefficient of CS solar cells improves with an increase in band discontinuities. Interestingly, contrary to the trends related to efficiency, our results indicate that the temperature coefficient of CS solar cells is more critically affected by the interface quality of the minority carrier extraction layer than the majority carrier extraction layer. These insights have important implications towards the choice of optimal material and processing conditions for Si based CS solar cells.

Published
2018
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19. Modeling based screening for optimal carrier selective material for Si based solar cells

Author

Chatterji, Nithin, Antony, Aldrin, and Nair, Pradeep R.

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science
Abstract

Carrier selective (CS) silicon solar cells are increasingly explored using a variety of different materials. However, the optimum properties of such CS materials are not well understood. In this context, through detailed analytical and numerical modeling, here we provide several interesting insights on the efficiency tradeoff with CS material properties. First, we show that perfect band alignment is a desirable feature only if the interface is devoid of any trap states. Otherwise, a band offset of around 0.2eV-0.4eV provides sufficient band bending to reduce the effect of interface recombination, thus improving the performance. Surprisingly, the interface passivation quality for the minority carrier extraction layer is found to be far less demanding than that for the majority carrier extraction layer. Additionally, doping density and dielectric constant of CS layers have a similar effect as band offset on solar cell performance. Our results have obvious implications toward the selection of appropriate materials as carrier selective layers and hence are of broad interest to the community., Comment: 12 pages, 11 figures and 1 table

Published
2017

29. Solid electrolyte membranes with Al2O3 nanofiller for fully solid-state Li-ion cells.

Author

Wilson, Merin K., Augustin, Cyril, Abhilash, A., Jinisha, B., Antony, Aldrin, Jayaraj, M. K., and Jayalekshmi, S.

Subjects
SOLID electrolytes, LITHIUM-ion batteries, SUPERIONIC conductors, POLYELECTROLYTES, FILLER materials, IONIC conductivity, ALUMINUM oxide, ALUMINUM-lithium alloys
Abstract

Fully solid-state lithium-ion cells have the benefits of excellent safety, remarkable electrochemical stability, and extended cycle life. They are categorized as prospective candidates for new-generation energy storage devices capable of safe and stable operation for relatively long periods. In whole solid-state Li-ion cells, polymer-based solid electrolyte membranes (SEMs) are expected to serve as both the solid electrolyte and the partition material. Remarkably high ionic conductivity and efficient ion diffusion can be achieved in SEMs by incorporating inorganic filler materials. In the present work, solid electrolyte membranes are developed by a simple solution cast method. The addition of Al2O3 nanoparticles is found to enhance the ionic conductivity of SE membranes to 1.25 × 10−4 S cm−1 for optimum concentrations of lithium salt and filler material. These SE membranes show relatively high electrochemical stability window up to 4.75 V. Transparent and freestanding SE membranes developed using PEO-PVDF-LiNO3-Al2O3 have excellent thermal stability, ideal ion transport number, and good electrochemical properties, suitable for applications in solid-state lithium-ion cells. Assembled LiFePO4-MWCNT//SEM//Li metal half-cells are found to deliver an initial discharge capacity of 128 mAh g−1 at 0.1 C and an initial Coulombic efficiency of 98%. [ABSTRACT FROM AUTHOR]

Published
2024
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38. Optically tuned low temperature processed silicon nitride and oxynitride multilayer antireflection coatings for crystalline silicon solar cells.

Author

Soman, Anishkumar and Antony, Aldrin

Subjects
*ANTIREFLECTIVE coatings, *SILICON solar cells, *PHOTOVOLTAIC power systems, *SILICON nitride, *LOW temperatures, *OPEN-circuit voltage, *REFRACTIVE index
Abstract

Design of multilayer anti-reflection coating (ARC) to reduce reflection losses from the surface of crystalline silicon solar cells requires materials having a wide range of refractive indices. In this paper, we use a series of low temperature (200°C) processed silicon-rich silicon nitrides and oxynitrides having optically engineered refractive indices for fabricating bi, tri and Rugate ARCs. We demonstrate that these multi-layer systems not only reduce the reflection losses for improved current collection but also have superior passivation properties to increase open-circuit voltage in silicon solar cells. The tri-layer ARC reduces the weighted average reflectance by 4.5% as compared to single ARC along with a minority carrier lifetime of 425 µs and implied voltage of 657mV making it a promising candidate as ARC for silicon solar cells. [ABSTRACT FROM AUTHOR]

Published
2023
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39. Fabrication of MoOx/c-Si/MgOx carrier selective heterojunction solar cell.

Author

Babu, Sneha, Sreena, S., Sharon, Antony, Rameeja, T. A. R., and Antony, Aldrin

Subjects
PHOTOVOLTAIC power systems, SOLAR cells, SILICON solar cells, HETEROJUNCTIONS, OPEN-circuit voltage, SPIN coating
Abstract

In recent years, the photovoltaic community has been paying much interest to solar cells with dopant-free carrier selective contacts. In such solar cells, the collection of carriers is achieved by introducing a band offset due to the asymmetry in band alignment with silicon. These dopant-free carrier selective contacts can be deposited on c-Si through simple, low-temperature techniques such as evaporation, spin coating, spray pyrolysis, etc. This work demonstrates the carrier selective potential of MoOx and MgOx films by fabricating Au/MoOx/n-Si/Ag and Al/MgOx/p-Si/Au heterojunction diodes, respectively. Both heterojunction structures showed good diode behavior in the dark. Then we fabricated a double heterojunction carrier selective solar cell with MoOx (where x is slightly less than 3) as the hole-selective layer (HSL) and MgOx/Al stack (where x is slightly less than 1) as the electron-selective layer (ESL) on the front and rear side of a planar n-type c-silicon substrate. The thermal evaporation technique was chosen for the deposition of MoOx and MgOx, as a low-cost fabrication method for the crystalline silicon solar cell. ITO was used as the transparent front contact, over which the Ag grid was deposited. The performance of the fabricated Ag/ITO/MoOx/n-Si/MgOx/Al double heterojunction solar cell was analyzed. A power conversion efficiency of 3.73 % was obtained with a short-circuit current density of 20 mA/cm2 and an open-circuit voltage of 410 mV. [ABSTRACT FROM AUTHOR]

Published
2023
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40. Colorimetric sensing of glucose using plasmonic gold nanoparticles.

Author

Saramgi, C. S., Subha, P. P., and Antony, Aldrin

Subjects
GOLD nanoparticles, SURFACE plasmon resonance, GLUCOSE, NANOPARTICLE synthesis, BLOOD sugar, GLUCOSE analysis, METAL nanoparticles
Abstract

Colorimetric sensors are extensively explored class of optical biosensors due to the visible eye detection enabled by them. An efficient way of colorimetric sensing can be achieved by studying the surface plasmon resonance (SPR) properties of noble metal nanoparticles like gold, silver etc. The SPR band of gold nanoparticles is influenced not only by their size and shape but also by the dielectric properties of the environment and the proximity of other nanoparticles which make them most suitable candidates for colorimetric sensing applications. In this work, we developed a novel, rapid, enzyme free colorimetric assay for glucose level determination. The normal levels of glucose in human blood range from3.8 to 6.9 mM approximately, although these levels may change during the day, being lower upon fasting and reaching a peak in post-cenal states. Both high and low glycemic levels are detrimental for health status. Glucose of various physiological concentrations (3 mM-50 mM) acts simultaneously as reducing and capping agent for the gold nanoparticle synthesis from tetrachloroauric acid enabling its label free detection. The increase in glucose concentration from normal to diabetic range cause a colour change from blue to red. The localized surface plasmon resonance (LSPR) peak is shifted from 520 to 580 nm due to the agglomeration of gold nanoparticles at lower concentrations of glucose. [ABSTRACT FROM AUTHOR]

Published
2023
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41. Polyaniline wrapped graphene quantum dot decorated strontium titanate for robust high-performance flexible symmetric supercapacitors.

Author

Joy, Rosmy, Wilson, Merin K, Antony, Aldrin, Konkena, Bharathi, Padmanabhan, Sibu C, Morris, Michael A, and Haridas, Suja

Subjects
POLYANILINES, QUANTUM dots, SUPERCAPACITORS, ENERGY density, GRAPHENE, POWER density, STRONTIUM titanate, TITANATES
Abstract

Design and development of promising electrode materials for supercapacitors has been a vital topic of current research focus. Here, we report the supercapacitive performance of the strontium titanate–graphene quantum dot–polyaniline heterohybrid. The synthesis strategy involves a sequential sol–gel synthesis of strontium titanate, followed by hydrothermal aided interface formation with graphene quantum dots (GQD) and polyaniline (PANI) deposition by chemical oxidative polymerization. A high specific capacitance of 2134 F g−1 could be observed in 1 M H2SO4 electrolyte at a current density of 1 A g−1. The Ragone plot for the symmetric cell reveals an energy density of 16.2 W h kg−1 at a power density of 4533.7 W kg−1. The 97.7% retention of specific capacitance demonstrated at higher current densities ensures high rate capability. Further, the device demonstrated a capacitance retention of 80% at 10 A g−1 after 10000 galvanostatic charge–discharge cycles. Low interfacial charge transfer resistance as evidenced by impedance spectroscopy analysis and high performance could be attributed to the synergistic interaction at the interface. [ABSTRACT FROM AUTHOR]

Published
2023
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46. Resistive switching in ZnO/MoOx bilayer for non-volatile memory applications.

Author

Manoj, Sandra, Sharon, Antony, Subin, P. S., and Antony, Aldrin

Abstract

Memory technologies are essential for transferring and preserving data. As the digital age progressed, memory device size, speed and efficiency were tuned to address the new demands. Resistive random access memory (RRAM) devices are promising candidates for future memory applications and have many advantages, such as scaling, speed, and endurance over conventional flash memory. In this work, bilayer metal oxide (MoOx/ZnO) devices are fabricated with Ag and ITO as top and bottom electrodes and their resistive switching characteristics are investigated for non-volatile memory applications. I–V characteristics of the device are analysed for the characteristic pinched hysteresis loop where bipolar switching has been observed with set voltage at 1.1 V and reset voltage at - 0.8 V. The field-dependent migration of oxygen vacancies in metal oxide layers accounts for the bipolar switching mechanism. The conduction mechanism for ITO/ZnO/MoOx/Ag device is studied, revealing ohmic conduction in the low voltage region while space charge limited conduction dominates in the high voltage region. Furthermore, the fabricated device shows excellent retention. Conclusively, this study suggests that the device switches at comparatively lower voltages and has remarkable data retention properties with the addition of MoOx layer over ZnO layer. Since the device shows excellent endurance and data retention properties, the fabricated device can be a good candidate for non-volatile memory applications such as RRAM and neuromorphic computing. [ABSTRACT FROM AUTHOR]

Published
2023
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