Solution processed polymer light-emitting diodes with single layer graphene anode

We fabricated the graphene based PLEDs that had the structure of glass / single layer graphene with Ag auxiliary electrode (anode) / PEDOT:PSS (HITL) / SPG-01T(Green polymer lighting material from Merck, EML) / Ca (EIL) / Al (Cathode). Single layer graphene was synthesized on copper foil by thermal CVD process, and then transferred to glass substrate by PMMA stamp. Formation of single layer graphene was confirmed from AFM, Raman spectroscopy, and UV-vis spectroscopy measurements. Graphene film was treated through a shadow mask for 15 minutes in UV ozone chamber to obtain anode pattern. After that, the patterned graphene layer was exposed to UV ozone to control its work function, which was found to be increased by 0.18eV and 0.27eV after 2.5 minutes and 5 minutes treatment, respectively. On the graphene layer, PEDOT:PSS and SPG-01T were consecutively spin-coated and annealed in the globe box. Ca and Al metal layer was deposited by thermal evaporation. Our graphene based PLEDs had the current efficiency of 9.73 cd/A and the power efficiency of 5.51 lm/W while our reference device with ITO anode showed the efficiencies of 12.5 cd/A and 8.01 lm/W.