Control of the surface composition of a conducting-polymer complex film to tune the work function

Control of surface composition of a hole-injecting conducting polymer complex, poly(3,4-ethylenedioxy thiophene) (PEDOT) doped with a polystyrene sulfonate (PSS) has been conducted in the spin-cast films. We found that the work function of the polymeric complex films formed via single spin-coating can be greatly increased up to 5.44eV by increasing the surface concentration of the PSS dopant. As a result, we improved the device efficiency and the lifetime of green emitting polymer light-emitting diodes (PLEDs). This implies that the PSS surface layer of the films spin-cast from the conducting polymer complexes plays a key role in making high performance PLEDs.