Doping effect of tetrathianaphthacene molecule in organic semiconductors on their interfacial electronic structures studied by UV photoemission spectroscopy

The n-type doping ability of the electron-donating organic molecule tetrathianaphthacene (TTN) was examined by ultraviolet photoemission spectroscopy (UPS) for two kinds of matrix organic semiconductors, hexadecafluorophthalocyaninatozinc (F16ZnPc) and tris(8-hydroxyquinoline)aluminum (Alq(3)). The observed dependence of the UPS spectra suggests that TTN acts as a good donor in F16ZnPc, while the effect was not so significant for Alq(3). These results and the consideration of the energy parameters of these molecules indicate that a close match between the highest occupied molecular orbital of the dopant and the lowest unoccupied molecular orbital of the matrix is important for efficient n-type doping.