Tuning the Work Function of Graphene-on-Quartz with a High Weight Molecular Acceptor

Abstract

Ultraviolet and X-ray photoelectron spectroscopies in combi- nation with density functional theory (DFT) calculations were used to study the change in the work function (Φ) of graphene, supported by quartz, as induced by adsorption of hexaazatriphenylene−hexacarbonitrile (HATCN). Near edge X-ray absorption fine structure spectroscopy (NEXAFS) and DFT modeling show that a molecular-density-dependent reorientation of HATCN from a planar to a vertically inclined adsorption geometry occurs upon increasing surface coverage. This, in conjunction with the orientation- dependent magnitude of the interface dipole, allows one to explain the evolution of graphene Φ from 4.5 eV up to 5.7 eV, rendering the molecularly modified graphene-on-quartz a highly suitable hole injection electrode

The role of gap states on energy level alignment at an α-NPD/HAT(CN) 6 charge generation interface

“…The threshold ionization potential (IP th ) of the present 15-nm-thick a-NPD films is 5.4 eV, similar to other published results [20]. On the other hand, the HOMO onset of 15-nm-thick HAT(CN) 6 on ITO substrate is at 3.7 eV, with the IP th of 9.3 eV, which agrees with the value reported by Christodoulou et al [21], indicating the standing up orientation of HAT(CN) 6 in the present HAT(CN) 6 films. Fig.…”

“…3(b) also show N 1s peaks from HAT(CN) 6 and a-NPD. The N 1s peak at 400.3 eV comes from HAT(CN) 6 , which consists of two N 1s components (AN@ group and C"N group) [21]; and the peak at 399.6 eV is from a-NPD [24]. Moreover, no obvious new peaks are found in Fig.…”

Facile Doping and Work‐Function Modification of Few‐Layer Graphene Using Molecular Oxidants and Reductants

“…[72] Increasing the concentration of dopants can either cause more clustering of dopants [79] -as we have observed in Figure 6b and 6c -or change their orientation and can even promote the layer-by-layer growth of multilayered structures, which we suspect is occurring in Figure 6d. [80] Layering of the dopant may decrease the likelihood of forming additional charged impurity scattering centers and may in fact decrease the scattering as compared to FLG doped for 60 min as the dopants would lie farther from the graphene surface due to dopant-dopant interactions, which would explain the increase in mobility at this stage. Surprisingly, the transport measurements ( Figure 5) show a decrease in carrier densities at higher dipping times despite a higher surface coverage of dopant species.…”

An analytical model for optimizing the performance of graphene based silicon Schottky barrier solar cells

“…Graphene also possesses excellent chemical and physical stability with a tunable work function [9][10][11]. Furthermore, graphene/silicon (G/Si) structure has been studied and shows diode characteristics as a Schottky junction [12].…”