| 초록 |
To achieve efficient electron injection in organic light-emitting diodes, we employed ultrathin cathode underlayers of the organic compounds (M-acetate, M-benzoate, Li-acetoacetate, Li-acetylacetonate, Li-t-butylcyclopentadienide) containing low work function alkali metals (M : Li, Na, K, Cs) between the emitting layer (Alq3) and the Al cathode. All devices with the 1.0 nm-thick cathode underlayers showed better performance than that with the conventional LiF layer except for the Cs-acetate layer. However, the best device performance was achieved when the Cs-acetate layer thickness was controlled to be ~ 2.0 nm. Especially, the device with the Li-acetylacetonate layer (1 nm) gave the power efficiency (ηp) of about 1.20 lm/W which is twofold higher than that with the LiF layer at the applied voltage of 12.5 V. The effectiveness of electron injection seems to be closely related to the formation, structure, and thickness of the alkali metal layer. |
