Red and Near-Infrared Electroluminescences from Metal-Free Phthalocyanine

Organic light emitting diodes are fabricated based on metal-free phthalocyanine (H₂Pc) doped into tris-(8-hydroxyquinoline) aluminium (Alq₃). The device structure is ITO/NPB (30nm)/Alq₃: H₂Pc(30nm)/BCP(20nm)
/Alq₃(20 nm)/Al. In the light-emitting layers, H₂Pc concentrations are varied from 0wt% to 100wt%. The emissions around 708nm and 800nm appear at low concentrations, while the emissions around 910nm and 930nm appear at high concentrations. The emissions around 708nm and 800nm are from H₂Pc monomers. The emissions around 910nm and 930nm are from H₂Pc aggregates. The dominant mechanism in the doped devices is direct charge
trapping.