Electronic structure of interfaces between copper-hexadecafluoro-phthalocyanine and 2,5-bis(4-biphenylyl) bithiophene

Abstract
The interfaces formed between copper-hexadecafluoro-phthalocyanine ( F 16 Cu Pc ) and 2,5-bis(4-biphenylyl) bithiophene (BP2T) were examined using photoemission and inverse photoemission spectroscopy. It is observed that in F 16 Cu Pc ∕ BP 2 T the heterojunction is characterized by band bending in both materials, while in BP 2 T ∕ F 16 Cu Pc the band bending is confined in BP2T only. The combination of the band bending and finite Debye lengths provides an explanation to the observed ambipolar behavior of the organic thin film transistors based on such heterojunctions.