[Study of poly (3,4-ethylene dioxythiophene) : poly (styrene sulfonate) by in-situ resonance Raman spectroscopy]

Poly (3,4-ethylene dioxythiophene) (PEDOT): Poly (styrene sulfonate) (PSS) has attracted a lot of interest for application in organic electronics due to good stability and high electronic conductivity in its doped state. Indeed, thin layers of PEDOT:PSS was regularly used in light emitting diodes (PLEDs) as hole injection and transportation layer. Here, Doping and dedoping states of PEDOT:PSS were studied by absorbance spectra and Raman spectra. A new absorption band centered at 620 nm was observed on dedoped PEDOT:PSS. Consistently, Raman signals of dedoped PEDOT:PSS are resonantly intensified since the Raman excitation wavelength (633 nm) is set in the enhanced absorption band. So it gives a sensitive way to study the doping and dedoping states of PEDOT:PSS. Furthermore, for the encapsulated polymer light-emitting diodes, Raman spectroscopy is a powerful way to study the polymer layers inside the devices.