We present an investigation of polymer light-emitting diodes (PLEDs) with a solution-processable graphene oxide (GO) interlayer. The GO layer with a wide band gap blocks electron transport from an emissive polymer to an ITO anode while reducing the exciton quenching between the GO and the active layer in place of poly(styrenesulfonate)-doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS). This GO interlayer maximizes hole-electron recombinations within the emissive layer, finally enhancing device performance and efficiency levels in PLEDs. It was found that the thickness of the GO layer is an important factor in device performance. PLEDs with a 4.3 nm thick GO interlayer are superior to both those with PEDOT:PSS layers as well as those with rGO, showing maximum luminance of 39 000 Cd/m(2), maximum luminous efficiencies of 19.1 Cd/A (at 6.8 V), and maximum power efficiency as high as 11.0 lm/W (at 4.4 V). This indicates that PLEDs with a GO layer show a 220% increase in their luminous efficiency and 280% increase in their power conversion efficiency compared to PLEDs with PEDOT:PSS.