The spectral sensitivity of PEDOT:PSS films

The sheet resistance of bare and encapsulated PEDOT:PSS films is investigated as a function of time when irradiated. A spectral sensitivity curve is extracted by monitoring the increase in sheet resistance over 500 h while the films are exposed to monochrome light in the spectral range of 290–417 nm at a power level of approximately 2 W/m². It is shown that light of wavelength λ<315 nm has to be strictly omitted to maintain the film's sheet resistance. The degradation can be significantly slowed down by taking proper encapsulation means. The impact of oxygen and humidity has to be blocked to avoid light induced oxidation reactions of PEDOT and subsequent conductivity losses. Alternatively, the conductivity can be maintained by the addition of stabilizing agents to the polymer dispersion.

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► PEDOT:PSS films loose conductivity when exposed to UV-light of λ<315 nm.
► The degradation can be significantly slowed down by proper encapsulation against air, by UV-protection layers, or by the addition of stabilizers.
► UV-exposure triggers the oxidation of the thiophene ring.