  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.
