Study on n-type Doped Electron-Transporting Layers in OLEDs by Electron Spin Resonance

Abstract

We present an electron spin resonance (ESR) study of Cs₂CO₃ and LiF doped tris(8-hydroxyquinoline) aluminum (Alq₃) thin films. The g values of the Cs₂CO₃ and LiF doped Alq₃ thin films were obtained as 2.0040 and 2.0028, repectively. The g value of the LiF doped film was very close to a theoretically calculated one for an isolated Alq₃ radical anion, while Cs₂CO₃ doped film showed a large g shift. This feature can be explained by large spin-orbit interaction caused by heavy Cs atoms. While doping of Cs₂CO₃ did not showed cathode-metal (Al and Au) dependence, LiF doping required Al as cathode.

Keywords:

• organic light-emitting diodes
• electron spin resonance
• doping
• electron-transporting layer
• charge transfer

Acknowledgments

This work was partly supported by a Grant-in-Aid for Scientific Research (24560004) from JSPS and by JST, PRESTO.