Executive Summary : | Nanostructured metal chalcogenides are the key materials for upcoming energy conversion and energy storage applications. A group of chalcogenides that has drawn interest in recent times is the II-VI chalcogenide family that includes zinc selenide (ZnSe) and zinc telluride (ZnTe). Nanostructured ZnSe and ZnTe have drawn attention over past 3 decades as heavy metal-free semiconductor nanocrystals with primary focus on LED and blue/green laser applications. But low electrical conductivity and fast recombination kinetics of photogenerated charge carriers restrain the application of these materials in electronic. Over last decade it has been demonstrated that chalcogenides dispersed in reduced graphene oxide (RGO) matrix can overcome such limitation. Besides working as a moderately charge conducting matrix, RGO-ZnSe/ZnTe possess excellent photoresponse and mobility enhancement under white light illumination. A variety of options to prepare RGO based chalcogenide composites exists that includes chemical synthesis of chalcogenides with simultaneous reduction of graphene oxide, tailoring quantum dots in RGO matrix through zeta potential tuning, solution route dispersion of cryoexfoliated chalcogenides QDs in RGO matrix and so on. In each case, plasma treatment can be effective in passivating defects in both RGO matrix and zinc-chalcogenide particles. Thermoelectric power generation from RGO and RGO based composite material is gaining interest in recent times owing to their moderate to high electrical conductivity and high degree of phonon scattering, resulting in moderate (~10-3) figure of merit (ZT). Recent computational studies predict a high ZT (0.141) for p-doped ZnSe for an optimal doping level. An RGO-ZnSe/ZnTe composite will have a higher electrical conductivity, as well as photo enhanced thermoelectric power generation capability, that would result in an even better ZT value. Herein, we propose to fabricate RGO-zinc chalcogenide-based field effect transistor (FET) arrays that can act as optical switch. Major limitation for such device being slow switching (on-off) time. To that aim, we plan to reduce the device size substantially by extensive use of optical and e-beam lithography, that will not only enhance the photocurrent, but will also improve the switching speed of the devices and reduce power consumption. Finally, the same device in a scaled-up configuration may be used as a photo-assisted thermoelectric power generator from waste heat of a car exhaust or a motor body. We plan to use the outcome of this project to fabricate scaled up opto- and thermoelectric devices for practical applications. |