Electric Conduction of Electroluminescent Metal Chelate Thin Films

Abstract Electric conduction in vacuum-deposited films of electroluminescent metal-chelates, tris-(8-hydroxyquinoline) aluminum (Alq3) and zinc bis-(2-(o-hydroxypheyl)-benzoxazolate)) (ZnPBO), were studied by current (I)-voltage (V) measurement. The I-V characteristics demonstrated that the films exhibited trap-controlled conduction. For the Alq3 film, conductivity σ was estimated to be 3.0 × 10−15 Scm−1 from the characteristic in ohmic current region. From the I-V characteristic in space charge limited current region, further, carrier mobility μ of the Alq3 film was estimated to be 5.0 × 10−7 cm2V−1s−1; this value is in good agreement with electron mobility evaluated by the time-of-fight technique. For ZnPBO, the values of σ and μ were estimated to be 2.0 × 10−14 Scm−1 and 7.0 × 10−6 cm2V−1s−1, respectively.