Cross-linking of a poly(3,4-ethylene dioxythiophene):(polystyrene sulfonic acid) hole injection layer with a bis-azide salt and the effect of atmospheric processing conditions on device properties

We investigate the role of atmospheric conditions during processing when cross-linking a poly(3,4-ethylene dioxythiophene):(polystyrene sulfonic acid) hole injection layer with a bis-azide salt. In particular, we investigate nitrogen atmosphere and air, since there is a competing reaction of the cross-linker with oxygen. We show enhanced work function when processing under inert conditions, with device properties otherwise unaffected. When processing is done in air, higher irradiation dosages are needed to cross-link and the resulting films show lower work functions. Surprisingly, the finished devices display an unexpected two-fold increase in efficiency which we attribute to increased electron trapping in these films. (C) 2012 American Institute of Physics. [doi:10.1063/1.3680606]