Mechanisms of Performance Improvement for Polymer Light-Emitting Diodes Fabricated on (NH4)2Sx-Treated Indium-Tin Oxide Substrates

[[abstract]]Photoelectron spectroscopy measurements show that (NH4)2Sx surface treatment may lead to an increase in the work function of indium-tin oxide (ITO), due to the occupation of oxygen vacancies (VO) by sulfur and a reduction in the amount of VO near the ITO surface region. Comparison between the current-luminance-voltage characteristics of polymer light-emitting diodes fabricated on ITO substrates with and without (NH4)2Sx treatment, shows that (NH4)2Sx treatment led to the enhancement of external quantum efficiency, due to the reduction of forward-biased leakage current (resulting from the reduction of VO-related defects near the ITO surface region)