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 epsilon = 3.16 x 10(-11) F m-1; hole mobility mu almost-equal-to 6.05 x 10(-10) m2 V-1 s-1; room temperature hole concentration p0 almost-equal-to 1.60 x 10(18) m-3; concentration of traps per unit energy range at the valence band edge P0 almost-equal-to 2.79 x 10(43) J-1 m-3; temperature parameter of trapping distribution T(t) almost-equal-to 770 K; total trap concentration N(t) almost-equal-to 2.97 x 10(23) m-3. The room temperature electrical conductivity sigma = 1.55 x 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.