Transparent and conductive nanocomposite films were spin-coated with the use of undoped and dimethyl sulfoxide (DMSO)-doped polyaniline (PANI)-poly(styrene sulfonate) (PSS) dispersions. The prepared dispersions were investigated in terms of their nanoparticle size distributions, and the corresponding films were morphologically, optically, and electrically characterized. These films were used as hole-injection layers (HILs) in organic light-emitting diode (OLEDs), and the device performances were compared to a reference device without an HIL. The device based on the PANI PSS layer showed the best electrooptical characteristics, lowest switch-on voltage, and improved efficiency. In particular, the device efficiency grew about three times with the introduction of the PANI PSS layer (1.20 Cd/A) and about two times with the introduction of the DMSO-doped PANI PSS film (0.77 Cd/A) compared to an OLED without an HIL (0.4 Cd/A). These results indicate that the device with the undoped PANI PSS was the more suitable one to be used as an HIL in an OLED device. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 3618-3623, 2011