Multi-color emission of polymer light-emitting diodes with multi-layer structure

Polymer light-emitting diodes, which possess a multi-layer structure and produce blue, green and red emissions on an ITO substrate, were successfully fabricated. The basic device structure is ITO/PEDOT/blue polymer/Ba/Al/green polymer/Ba/Al/red polymer/Ba/Al, where PEDOT is poly(styrene sulfonic acid), functioning as the hole transportation, injection, and ITO surface modification, Ba: barium electron injection cathode, Al: aluminum, acting as the protecting layer from Ba oxidized. All polymer layers were prepared by spin-coating technique. The blue, green and red emission intensities can separately be controlled. Possible electroluminescence (EL) mechanisms were discussed in this paper.