Researchers from King Abdullah University of Science and Technology (KAUST), in collaboration with the Georgia Institute of Technology, have recently demonstrated a simple, solution-based, method for surface doping of few-layer graphene (FLG) using novel dopants (metal-organic molecules) that show a minimal effect on the optical transmission as compared to other dopants like metal chlorides.
This work investigates the effect of dopant strength and dosage on the electronic and electrical transport properties of doped FLG. Moreover, It reveals fundamental differences between the doping results in single layer graphene and few-layer graphene. The study focused on few-layer CVD graphene, rather than single-layer CVD graphene, a somewhat less common area of research to date.
The team states that it offers a versatile and facile doping approach of few-layer graphene towards TCE applications (transparent conducting electrode), which could open the door to the commercialization of graphene as a replacement for ITO in electronics and optoelectronics, in applications like touchscreens, by increasing the Figure-of-Merit and offering a large range of work function tunability.
In this work, the researchers tuned the electronic, optical, and transport properties of FLG. They modulated the work function of graphene over a range of 2.4 eV (from 2.9 to 5.3 eV) via surface electron transfer. A substantial improvement of the conductivity of FLG is attributed to increasing carrier density, slightly offset by a minor reduction of mobility via Coulomb scattering. The mobility of single layer graphene has been reported to decrease significantly more via similar surface doping than FLG. The dopant dosage influences the properties of FLG and reveals an optimal window of dopant coverage for the best transport properties, wherein dopant molecules aggregate into small and isolated clusters on the surface of FLG. This study shows how soluble molecular dopants can easily and effectively tune the work function and improve the optoelectronic properties of graphene.