Reducing sheet resistance of self-assembled transparent graphene films by defect patching and doping with UV/ozone treatment

TL;DR

This paper presents a UV/ozone treatment that reduces sheet resistance and enhances conductivity of self-assembled graphene films without compromising transparency, improving their suitability for transparent conductor applications.

Contribution

The study introduces a novel UV/ozone photochemical treatment that decreases defects and dopes LBSA graphene, significantly lowering sheet resistance and advancing scalable transparent conductor production.

Findings

UV/ozone reduces defect density in LBSA graphene

Treatment triples the reduction in sheet resistance

Doping increases film conductivity

Abstract

Liquid phase exfoliation followed by Langmuir-Blodgett self-assembly (LBSA) is a promising method for scalable production of thin graphene films for transparent conductor applications. However, monolayer assembly into thin films often induces a high density of defects, resulting in a large sheet resistance that hinders practical use. We introduce UV/ozone as a novel photochemical treatment that reduces sheet resistance of LBSA graphene threefold, while preserving the high optical transparency. The effect of such treatment on our films is opposite to the effect it has on mechanically exfoliated or CVD films, where UV/ozone creates additional defects in the graphene plane, increasing sheet resistance. Raman scattering shows that exposure to UV/ozone reduces the defect density in LBSA graphene, where edges are the dominant defect type. FTIR spectroscopy indicates binding of oxygen to the graphene lattice during exposure to ozone. In addition, work function measurements reveal that the treatment dopes the LBSA film, making it more conductive. Such defect patching paired with doping leads to an accessible way of improving the transparent conductor performance of LBSA graphene, making solution-processed thin films a candidate for industrial use.