Voltage‐tunable‐color multilayer organic light emitting diode

Organic electroluminescent diodes with a double‐heterostructure of indium‐tin‐oxide (ITO) substrate/aromatic diamine (TPD)/8‐hydroxyquinoline aluminum (Alq3)/perylene bisimide pigment (PBP)/Mg/Ag have been fabricated by successive vapor deposition. Their electroluminescence (EL) for thin layers of PBP varies from the orange dominated by the red emission of PBP to greenish‐yellow with a strong contribution of the green emission of Alq3 as voltage increases. The relative contribution of the red emission increases with increasing voltage for the structures with thick PBP layers. The tuning of the EL color is explained in terms of electric field‐induced quenching of excited states and voltage evolution of the recombination zone in PBP.