Electric contacts on conductive polymers: sodium on poly(3-hexylthiophene-2,5-diyl)

Sodium as a model contact with low work function on regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) films was investigated. The interface was studied by X-ray and ultraviolet photoelectron spectroscopy in the range of 0.13 up to 1.8 metal atoms per hexylthiophene unit. In the range of 0.13–0.26 sodium atoms per hexylthiophene ring we find a change in the surface potentials which is interpreted as a discharge of positive surface charges. Sodium exposures above 0.5 sodium atoms per hexylthiophene unit exhibit a reduction of the thiophene sulfur due to the formation of sodium sulfide and breaking of the thiophene ring.