Electronic structure modification of Si-nanocrystals with F4 -TCNQ

We use first-principles models to demonstrate how an organic oxidizing agent, F4 -TCNQ (7,7,8,8- tetracyano-2,3,5,6-tetrafluoroquinodimethane), modifies the electronic structure of silicon nanocrys- tals, suggesting it may enhance p-type carrier density and mobility. The proximity of the lowest unoccupied level of F4 -TCNQ to the highest occupied level of the Si-nanocrystals promotes the formation of an empty hybrid state overlapping both nanocrystal and molecule, reducing the exci- tation energy to about 0.8-1 eV in vacuum. Hence, it is suggested that F4 -TCNQ can serve both as a surface oxidant and a mediator for hole hopping between adjacent nanocrystals.