We report a simple method involving mechanical attrition followed by hot press sintering to fabricate tablet samples consisting of silver nanoparticles (Ag NPs) dispersed in luminescent silicon nanocrystal (Si NC) matrix. A dramatic increase in current by almost six orders of magnitude is observed for this type of Si NC-Ag NP hybrid nanocomposite compared with bare Si NC-based tablets. Collective charge transport through such hybrid system exhibits unexpected and fascinating characteristics. On the other hand, a remarkable reduction in thermal conductivity by two orders of magnitude is observed in the Si NC-Ag NP nanocomposite compared with the bulk counterpart. This is due to the combined effect of reduction in thermal conductivity of individual NPs and enhanced phonon scattering at the interface. We have, therefore, successfully decoupled electrical and thermal conductivity, which is not possible in any bulk material. The huge increase in electrical conductivity with substantial reduction in thermal conductivity makes this hybrid system amenable for designing efficient thermoelectric with high thermoelectric figure of merit, which has remained a significant challenge.
Keywords: metal-semiconductor nanocomposite, silicon quantum dots, silver nanoparticle, electrical conductivity, thermal conductivity, thermoelectric.