Magneto-Conductance in Tri-(8-Hydroxyquinoline) Aluminum-Based Organic Light Emitting Diodes

The origin of magneto-conductance (MC) in tri-(8-hydroxyquinoline)-aluminum (Alq₃)-based organic light emitting diodes is investigated. Our results clearly show that the generated MC is related to the singlet polaron pair dissociation. Further studies on the MC in an electron blocking layer N,N'-bis(lnaphthyl)-N,N'-diphenyl-l,l'-biphentl-4,4'-diamine (NPB) and a hole blocking layer 2,2',2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole (TPBi)-based devices indicate that the holes reaching the cathode from the dissociation of singlet polaron pairs on Alq₃ are the main cause of the MC generation. It is found that the MC can be significantly reduced by doping a red fluorescence dye DCJTB as a hole trapper in Alq₃.