Correlating carrier concentration and mobility in graphene oxide-doped PEDOT:PSS with electroluminescence efficiency of polymer light-emitting diodes

We report a quantitative decoupling of carrier concentration and mobility in graphene oxide (GO)-doped poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and identify the dominant transport factor associated with electroluminescence (EL) efficiency in polymer light-emitting diodes. Combined Hall-effect and space-charge-limited current analyses reveal no systematic correlation between carrier concentration and device performance, whereas hole mobility exhibits a pronounced maximum at an optimal GO loading and closely follows the EL efficiency trend. This non-monotonic behavior is attributed to the competition between improved percolation pathways and disorder-induced carrier scattering. Despite minor variations in optical transmittance and work function, device performance is significantly improved, supporting the dominant role of effective vertical transport in device operation. GO incorporation optimizes effective injection/transport pathways and facilitates field-assisted hole transport into the emissive layer, which may contribute to more favorable recombination conditions. The optimized device achieves a maximum luminance of 3910 cd/m2 and a current efficiency of 2.48 cd/A, corresponding to an order-of-magnitude enhancement. These results establish mobility-governed effective vertical transport as a key mechanism and provide a physically grounded design principle for optimizing PEDOT:PSS-based optoelectronic devices.