Versatile p-Type Chemical Doping to Achieve Ideal Flexible Graphene Electrodes

We report effective solution-processed chemical p-type doping of graphene using trifluoromethanesulfonic acid (CF3SO3H, TFMS), that can provide essential requirements to approach an ideal flexible graphene anode for practical applications: i) high optical transmittance, ii) low sheet resistance (70% decrease), iii) high work function (0.83 eV increase), iv) smooth surface, and iv) air-stability at the same time. The TFMS-doped graphene formed nearly ohmic contact with a conventional organic hole transporting layer, and a green phosphorescent organic light-emitting diode with the TFMS-doped graphene anode showed lower operating voltage, and higher device efficiencies (104.1 cd A(-1), 80.7 lm W-1) than those with conventional ITO (84.8 cd A(-1), 73.8 lm W-1).