Research Projects

Currently, metal oxide based transparent conductors (TC) like indium tin oxide (ITO), florin doped tin oxide (FTO) is widely used in optoelectronics device like solar cell, photodetector LEDs etc. However, indium is not an earth abundant element which can fulfill the growing demand of ITO. Therefore, the cost of ITO is increasing very fast with time to fulfill the sharply increasing demand of TC. In such situations, there is an urgency to find an alternative of conventional ITO based TC. Moreover, due to the ceramic nature of ITO, it is not a very good choice for mechanically flexible optoelectronic devices. A good number of efforts are given for the development of different nanostructured based TC, including graphene and carbon nanotube, that have very good transparency with mechanical flexibility. Although their poor electrical conductivity limited their commercialization. Relatively metal-based TCs have higher conductivity with reasonably good transparency. Among different metals, Ag is most widely used element that can be used for fabricating TC, mainly due to its low refractive index (n~0.05 in the visible range). In the past, Ag has been used in form of nanowire or oxide/Ag/oxide multi-stack thin film for fabricating TC. These Ag-based TCs have higher electrical conductivity than ITO with acceptable mechanical flexibility, which could be an ideal TC electrode for flexible electronics. However, Ag nanostructured or Ag thin films have very strong plasmonic absorption, which is a key barrier to achieving high optical transparency of those films. Besides, due to higher reactivity of Ag nanostructures, long-term stability of these Ag-based TCs is not as good as ITO. In this proposal, Ag-Au bi-metallic plasmonic transparent conductor (PTC) thin films will be developed that could have optical transparency ~90% in the visible range with sheath resistance lower than that of commercial ITO. The processing temperature of such TC will remain within 100 oC, making it mechanically flexible PET substrate compatible. Also, deposition is possible on a large area substrate through a roll-to-roll coating method. This Ag-Au based bimetallic PTC will be used for developing high efficiency solar cell application as a replacement of conventional ITO. Besides, due to the contribution of plasmon induced hot-electron, particularly in NIR solar spectrum region, power conversion efficiency of this solar cell can be enhanced significantly. In addition, a high-performance NIR/IR photodetector will be fabricated using this bimetallic PTC with high detectivity and a very fast response. Besides, Ag based large area and mechanically flexible PTC will be developed that can be used as transparent heat reflector (THR). Such THR window coating can block IR/NIR and allow visible light to enter through the window. Therefore, this plastic based THR can be used as window cover of a building or car that can reduce the daytime electricity costof air condition (AC) as well as light.