Interaction between organic semiconductors and LiF dopant

X-ray photoemission spectroscopy and optical absorption have been used to study the interaction between LiF dopant and various organic semiconductor hosts including N,N′-diphenyl-N,N′-bis (3-methylphenyl)-1, 1′-biphenyl-4, 4′-diamine (TPD), N,N′-bis (1-naphthyl)-N,N′-diphenyl-1, 1′-biphenyl-4, 4′-diamine (NPB), tris (8-hydroxyquinolinato) aluminum (Alq3), C60, and copper phthalacyanine (CuPc). It was found that there is a charge transfer between host and dopant in the Alq3–LiF and C60–LiF systems, while no such charge transfer was observed for the TPD–LiF, NPB–LiF, and CuPc–LiF systems. The experimental data show that F− anion acts as an n-type donor—donating electron charge to the electron transport molecules.