Photocurrent multiplication phenomena at organic/metal and organic/organic interfaces

Photocurrent multiplication phenomenon due to the photoinduced tunneling injection of electrons at the organic/metal interface was intentionally invoked by changing the film structure of perylene pigment from amorphous to crystalline. This result can be reasonably explained based on the structural trap model. Imperfect contact between crystalline pigment film with microscopically rough surface and Au film has a large number of molecular-sized blind alleys (structural traps), which build up a high electric field at the organic/metal interface by accumulating the photogenerated holes and cause large multiplication. On the other hand, the photocurrent multiplication reaching 3000-fold was newly observed at an organic/organic heterojunction between p-type phthalocyanine and n-type perylyne pigment layers. Multiplied photocurrent caused upon the irradiation of red light exciting CuPc was effectively suppressed by irradiating blue light exciting Me-PTC simultaneously. (C) 1998 Elsevier Science S.A. All rights reserved.