An experimental study of poly 9,9-dioctyl-fluorene/and its interface with Li and LiF.

The chemical and electronic structure of a new conjugated polymer, poly 9,9-dioctyl-fluorene. PFO., has been studied by photoelectron spectroscopy. The polymer films were free of oxygen contamination within the detection limits of photoelectron spectroscopy.. X-ray and ultraviolet photoelectron spectroscopy was carried out on Li- and LiF-deposition on PFO as well as on LiF-deposition on aluminum. In the case of Li-deposition on PFO films, doping occurred resulting in the formation of polaronic charge carriers at low doping levels and bipolaronic charge carriers at high doping levels. LiF-deposition on PFO did not cause doping of the polymer films, nor did the LiF dissociate at the interface. No significant shifts in binding energy BE.or work function occurred. LiF-deposition on sputter-cleaned aluminum showed evidence of surface dipole formation, though LiF dissociation was not detected. Al-deposition on LiFrPFO films did not cause dissociation of LiF, unlike the case in Alq3. q2000 Elsevier Science B.V. All rights reserved.