2016 Volume 37 Issue 8 Pages 386-391
Metal/organic interfaces in organic thin-layer photovoltaic cells were investigated by means of hard X-ray photoelectron spectroscopy (HAXPES). The large detection depth of HAXPES using 6 keV X-rays allowed to study the buried organic layer, poly (3,4-ethylenedioxythiophene) : polystyrene sulfonate (PEDOT : PSS), through the Ag electrode. PEDOT : PSS showed two additional S 1s peaks at the Ag electrode interface, which could be associated with thiolate-like species and Ag sulfides. The latter peak increased after the high-humidity test, indicating that the interface reaction proceeded during the test. Severe X-ray-induced damage of PEDOT : PSS layer was also observed, mainly due to the transformation of sulfonate groups of PSS to the lower oxidation-state forms. Nevertheless, HAXPES showed to be one of the powerful tools to study the buried interface of organic devices as it is.
