Doping of organic semiconductors induced by lithium fluoride/aluminum electrodes studied by electron spin resonance and infrared reflection-absorption spectroscopy

摘要

We report our investigations on the chemical doping mechanisms induced by LiF|Al electrodes evaporated onto fullerene thin films. Electron spin resonance (ESR) and infrared reflection-absorption spectroscopy (IRRAS) are utilized to characterize C_(60)|A1 and C_(60)|LiF|Al interfaces. ESR spectra show that deposition of LiF followed by Al generates C_(60) radical anions and also the presence of an additional paramagnetic species of lower concentration that is present in all C_(60) films regardless of LiF. IRRAS clarifies the mechanism occurring at the C_(60)|LiF|Al interface, showing that interaction between LiF and C_(60) followed by deposition of Al causes LiF clusters to chemically dissociate.