Organic light-emitting devices based on conducting polymer treated with benzoic acid

We report on the enhanced conductivity of the benzoic-acid-treated poly(3,4-ethlenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) electrode for use in highly flexible, organic light-emitting devices (OLEDs). The conductivity of the benzoic-acid-treated PEDOT:PSS electrode increased from 1 to 1583.2 S/cm, in comparison with that of the pristine PEDOT:PSS electrode, due to a complex factor of the H⁺ mole % and the dielectric constant of the benzoic solution. Among the post-treatment methods of the PEDOT:PSS electrodes, the operating voltage at 1000 cd/m² of OLEDs fabricated utilizing the PEDOT:PSS electrode with the benzoic acid treatment has the lowest value, and its maximum luminance is 24,400 cd/m², which are 1.54 and 2.15 times higher than those of OLEDs using PEDOT:PSS electrodes treated with dimethyl sulfoxide and methanol, respectively. The luminance of a flexible OLED with a benzoic-acid-treated PEDOT:PSS electrode after 1400 bending cycles decreased to 83% of the initial luminance, resulting in excellent mechanical stability.