ABSTRACT
In this study, we report the effects of the substrate rotational speed on the morphological characteristics of lithium fluoride (LiF) during thermal evaporation. LiF is used as a typical material in a vacuum-level shift-based electron injection layer and can improve both the charge injection and light emission properties when inserted into the electrode/organic material interface of organic light-emitting diodes (OLEDs). In general OLED research, rotary evaporation is widely used to ensure uniformity. However, there are few reports regarding the effects of this rotary evaporation method on the morphological characteristics of the thin films. Therefore, in this study, we analyzed the effects of rotary variations on the morphological and electron injection characteristics during deposition. The root mean square roughness of the LiF thin film deposited on Alq3 changed by up to 12.3%. Additionally, the driving voltage of the electron-only device showed a difference of 2.3 V at maximum and a change in the slope of the ohmic region was demonstrated. The morphological change in the LiF thin film based on the rotational speed of the substrate had a significant influence on the reaction at the electrode/organic material interface.
