Photoinduced Hole Injection Multiplication in p-Type Quinacridone Pigment Films

Abstract
A large photocurrent multiplication due to hole injection reaching 2500-fold was observed in organic p-type quinacridone pigment films. This phenomenon was revealed to be due to photoinduced excess hole injection from a positively biased metal electrode to the p-type organic film through its depletion layer under a high electric field, which is built up by the photo-accumulation of trapped electrons near the interface. This is a clear example that the reverse mechanism to the photoinduced electron injection observed for n-type organic pigment film can occur in p-type organic pigment film.