The role of cesium fluoride as an n-type dopant on electron transport layer in organic light-emitting diodes

We report on the role of cesium fluoride (CsF) doping on the enhanced electron transport properties of tris-(8-hydroxyquinolin) aluminum (Alq3) for organic light-emitting diodes. The electronic structures of CsF-doped Alq3 layers with various doping concentration are characterized by in situ ultraviolet and X-ray photoelectron spectroscopies, showing an n-type electrical doping effect with Fermi level shift towards unoccupied molecular orbital and the formation of chemistry-induced gap-states. The increase in conductivity and reduction in electron injection barrier in CsF-doped Alq3 layer with optimal doping concentration lead to the enhanced electron injection and transport, which are consistent with the improved electrical characteristics of OLEDs.

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► Optimal doping of CsF leads to enhanced electron injection and transport in OLEDs.
► Doping effect of CsF in organic electron transport layer is studied by UPS and XPS.
► An n-type electrical doping effect is estimated with Fermi level shift towards unoccupied molecular orbital.
► CsF doping results in the chemistry-induced gap state due to the chemical bonding between CsF and Alq3.