Highly efficient hole injection from Au electrode to fullerene-doped triphenylamine derivative layer

Triphenylamine derivatives are superior hole-transport materials. For their application to high-functional organic semiconductor devices, efficient hole injection at the electrode/triphenylamine derivative interface is required. Herein, we report the design and evaluation of a Au/fullerene-doped alpha-phenyl-4'-[(4-methoxyphenyl)phenylamino]stilbene (TPA) buffer layer/TPA/Au layered device. It exhibits rectification conductivity, indicating that hole injection occurs more easily at the Au/fullerene-doped TPA interface than at the Au/TPA interface. The Richardson-Schottky analysis of the device reveals that the hole injection barrier (Phi(B)) at the Au/fullerene-doped TPA interface decreases to 0.021 eV upon using C-70 as a dopant, and Phi(B) B of Au/TPA is as large as 0.37 eV. The reduced Phi(B) of 0.021 eV satisfies the condition for ohmic contact at room temperature (Phi(B) <= 0.025 eV). Notably, C-70 doping has a higher barrier-reduction effect than C-60 doping. Furthermore, a noteworthy hole-injection mechanism, in which the ion-dipole interaction between TPA and fullerenes plays an important role in reducing the barrier height, is considered based on cyclic voltammetry. These results should facilitate the design of an electrode/organic semiconductor interface for realizing low-voltage driven organic devices.

Automated summary

This study investigates the effect of Au/fullerene-doped TPA interface on efficient hole injection, finding that using C-70 as a dopant can significantly reduce the hole injection barrier. The ion-dipole interaction between TPA and fullerenes is considered to play a role in reducing the barrier height based on cyclic voltammetry.