Electronic structure of hybrid interfaces of poly(9,9-dioctylfluorene)

In this Letter we report the results of a study of the energy level alignment at interfaces between ultra-thin films of poly(9,9-dioctylfluorene) and AlxOy, SiO2 or gold substrates, prepared under ambient (air) conditions. In all the cases, vacuum level alignment occurs, and the work function tracks that of the substrates. There is no evidence of band bending in the pristine polymer layers up to 1100 إ in film thickness. Upon increasing the electrical conductivity of the polymer films by continuous doping with sodium under ultra-high-vacuum conditions, the energy levels of the polymer film gradually shift towards higher binding energies and finally become substrate independent.