White polymer light emitting diodes with multi-layer device structure

White polymer light emitting diodes (WPLEDs) were fabricated with multi-layer device structure using crosslinked poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene] (MEHPPV) as a red emitting layer (EML) and crosslinked poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4″,4‴-tertbutyl-tetraphenyl diamine-4,4′-diyl) (PF8-tTPD) as a blue emitting layer. The multi-layer device structure was realized by crosslinking the emitting layers through ultra-violet (UV) irradiation. The results showed that the crosslinking of the emitting layer affected the carrier mobility of the polymer layer and the recombination site of the electrons and holes, therefore affected the emission of the devices. The devices with crosslinked MEHPPV as red emitting layer and crosslinked PF8-tTPD as blue emitting layer showed good white emission with C.I.E. coordinates (X: 0.364; Y: 0.290) at about 500 cd/m2 and showed good color stability with increasing applied voltages. UV irradiation method was found to be an effective way to crosslink the emitting layer and fabricate multi-layer polymer light emitting diodes (PLEDs).