Gas Sensors for Environmental Monitoring and Biomedical Applications
Gas Sensors for Environmental Monitoring and Biomedical Applications
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As atmospheric pollution has considerably increased in the recent years, detection of harmful and flammable gases is a subject of growing importance in both domestic and industrial environments. The focus of our research is on the development of sustainable gas sensor systems having high selectivity towards undesirable toxic gas species (e.g. NO2, NH3, H2, CO2, H2S, SO2 etc.) at lower operating temperature using nanoscale heterojunction materials based on Metal Oxide Semiconductors and Carbon Nanostructures by modulating the unique charge transport across material interfaces leading to development of nanosensor devices. We use in-situ/operando studies based on conducting probe microscopy and confocal Raman spectroscopy to unravel the mechanistic pathways of the sensing phenomena in heterojunction nanomaterials. For the nanopatterning and fabrication of nanosensor devices, we use mask-less lithography and chemical/physical vapour deposition techniques. Our group has recently developed a new class of temperature-independent oxygen sensors exploiting the Semiconductor-to-Metal Transition (SMT) and modulation of temperature coefficient of resistance (TCR) characteristics in mixed valent vanadium oxide (VOx) based nanosystems to address thermal drift in gas sensors in automobile exhaust emission control. Our group also developed hydrogen sensors based on cost effective, less-Pt bimetallic catalyst functionalized carbon nanofibers. The gas sensors developed in our laboratory can find their applications in pollution control, safety and leakage detection, biomedical applications etc.
PEM Fuel Cells
PEM Fuel Cells
At PSGIAS our group have successfully developed N-doped mesoporous carbon nanostructured materials (mesoporous carbon nanofibers (MPCNFs), nitrogen doped graphene foam (N-graphene foam) and mesoporous hollow carbon nanofibers (mPHCNFs)) with platinum nanoparticles as the electrocatalyst material as electrocatalyst support material for PEMFCs. The superior ORR performance exhibited by the developed electrocatalyst support materials are based on three major material design criteria, namely; (i) high surface area and surface activity for effective dispersion of metal nanoparticles as catalyst (ii) high conductivity for providing electrical pathways and N-doping of the carbon support materials, (iii) hierarchical porous structure from controlled size of micro/mesopores/hollow channels that facilitated smooth mass transport phenomenon. Electrocatalytic properties showed enhanced activity and excellent stability and performance evaluation of single PEM fuel cells have been completed. Currently, we are focusing on development of highly durable PEM fuel stack based on the developed materials for industry-ready technologies.
Self-cleaning coatings for PV & non-PV applications
Self-cleaning coatings for PV & non-PV applications
Superhydrophobic coatings based on nanoscale materials can lead to revolutionary solution for the performance loss of solar panels due to dirt accumulation. Being nanoscale, the superhydrophobic coatings does not interfere in the transparency of the solar panel surfaces. Coating of nanoscale superhydrophobic materials on large area solar panels is another challenging issue. At PSGIAS, we have developed transparent self-cleaning superhydrophobic (SH) coatings for solar panel cover glass applications. For this, two different approaches have been developed in our laboratory. The first approach is transparent, anti-reflective self-cleaning coating based on superhydrophobicity has been developed which exhibited ultrahigh water contact angle of >175o and near-zero roll-off angle <1o. Moreover, the developed coatings were found to exhibit anti-reflective property with an optical transmittance of >92%. Solar cell efficiency was improved by 2% as compared to the uncoated solar cover glass. In the second approach, a new SH coating formulation has been developed based on hybrid polymer/ceramic nanoparticles, which exhibited water contact angle >1550 and roll-off angle <50. The optical transmittance was found to be 88% in the visible region (400-800 nm). The stability of the coatings were tested with the standard testing instruments, such as accelerated weathering tester, sand abrasion tester, peel tester, scratch resistance tester and pencil hardness tester. Both SH coatings are durable and scalable above 1x1m2 and above and field trials at different locations and quality testing have been completed for commercialization purposes. These self-cleaning superhydrophobic coatings also have been extended for large area non-PV applications.
Silver-less (Ni-Cu-Sn) Narrow-Line Width Front Contact Metallization Patterns for Solar Cells
Silver-less (Ni-Cu-Sn) Narrow-Line Width Front Contact Metallization Patterns for Solar Cells
Screen printing is the most dominant technology used in solar cell industry for front and rare side metallization because of its high throughput. However, the utilization of silver is quiet high in screen printing compared to other methods and solar cell manufacturers through-out the globe are looking for alternate metallization technologies. In order to reduce the shadow loss in silicon solar cells, the finger width has to be narrowed down to <30 µm. High cost of silver paste and finger interruptions which generally arise during cell metallization process, module interconnections and lamination process are the major issues with existing conventional screen printing process, especially while fabricating high aspect ratio narrow-width finger lines. At PSGIAS, our group has developed cost-effective, silver-less fine-line width front contact metallization patterns for solar cells using nanoimprint lithography (NIL) and maskless lithography. As a part of this investigation, we have also developed a low cost, in-house nanoimprint lithography tool which can be successfully integrated with device manufacturing process of crystalline silicon solar cells. Based on our Finite Element Analysis (FEA) simulation studies, an optimized of solar cell front side metallization grid pattern was designed with which, the cell efficiency can be increased by ~1%, minimizing the shading loss. In this method, instead of using silver screen printing, Ni/Cu/Sn metallization was adopted for patterning metallization grids in silicon solar cells, as the conductivity of copper is comparatively equal to silver with a wider margin in the cost. Based on this method, significant reduction in the cost of the solar cell can be easily achieved with NIL/maskless lithography patterning of the fine-line width (<20 um) fingers in the metallization grids.
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