The effect of UV ozone treatment on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)

Abstract

The interface between ultraviolet (UV)ozone treated poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and N , N ′ -diphenyl- N , N ′ -bis-(1-naphthyl)-1- 1 ′ -biphenyl- 4 , 4 ′ -diamine ( α -NPD) was investigated using single carrier hole-only devices and in situ ultraviolet and x-ray photoelectron spectroscopy to elucidate the implications for device applications. It is found that although the work function of PEDOT:PSS is increased by UVozone treatment, the injection barrier to α -NPD is in fact increased, resulting in lower current density in devices. The apparent increase in work function is attributed to a metastablesurface dipole as a result of UVozone treatment, which does not significantly influence the energy-level alignment.