Concentration effect of glycerol on the conductivity of PEDOT film and the device performance

Poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT)-based polymeric electroluminescent (EL) devices using glycerol-modified poly(styrene sulfonate)-doped poly(3,4-ethylene dioxythiophene) (GPEDOT) films as anodes have been fabricated. By comparing the devices made with unmodified commercial PEDOT anode, glycerol doping effectively reduces the operating voltage. At a current density of 60 mA/cm2, the operating voltage for device with 0.28 g/ml GPEDOT anode greatly reduces to 7.8 V; while that for device with unmodified PEDOT anode is about 9.9 V. This is mainly attributed to the significant enhancement of conductivity by incorporating a suitable amount of glycerol into polymeric PEDOT layer. It was further found that the conductivity of PEDOT film increases with the concentration of glycerol doping. Therefore, this highly conductive polymeric anode can be finely tuned to have an optimized conductivity such that a better balance of electron and hole currents, and thus a better device efficiency, can be achieved.