Organic light-emitting diode with polyaniline-poly(styrene sulfonate) as a hole injection layer

In order to improve the performance of organic light emitting diodes (OLED), a water-dispersed polyaniline-poly(styrene sulfonate) (PANI-PSS) was used as a hole injection layer (HIL). The current–voltage and luminescence–current characteristics of the OLED devices were investigated as functions of PANI:PSS weight ratio and the kind of dopants. The PANI-PSS film coated on the indium–tin oxide showed a reduced surface roughness, higher work function, and improved transparency, compared to poly(3,4-ethylenedioxythiophene) (PEDOT)-PSS. In addition, PANI-PSS HIL led to a better operation voltage reduction (ca. 15%) and displayed a higher level of luminance performance (ca. 30%) than the commercial PEDOT-PSS system.