Ohmic and Space-Charge-Limited Conduction in Lead Phthalocyanine Thin Films

The electrical characteristics of thermally evaporated triclinic lead phthalocyanine thin films are studied. A number of parameters is evaluated on the basis of the theory of space-charge-limited conduction and the following values are obtained: permittivity ϵ = 3.16 × 10−11 F m−1; hole mobility μ ≈ 6.05 × 10−10 m2 V−1 s−1; room temperature hole concentration p0 ≈ 1.60 × 1018 m−3; concentration of traps per unit energy range at the valence band edge P0 ≈ 2.79 × 1043 J−1 m−3; temperature parameter of trapping distribution Tt ≈ 770 K; total trap concentration Nt ≈ 2.97 × 1023 m−3. The room temperature electrical conductivity σ = 1.55 × 10−10 S m−1. CU measurements confirm that the AuPbPc interface does not form a Schottky barrier. At low temperatures the capacitance of AuPbPcAu devices is temperature insensitive, increasing rapidly above 300 K and saturating at about 400 K. Measurements of thermoelectric power confirm that semiconduction is p-type.