Effect of LiF-Electron Injection Layer Thickness on Efficiencies of Organic Light Emitting Diode

摘要

The influence of charge injection on efficiency and operating voltage of organic light emitting device was investigated. Using UV-treated and un-treated ITO substrates, organic light emitting diodes were fabricated as we vary the thickness of LiF layer as the electron injection layer. The operating voltages and efficiencies were measured. When ITO surface is UV treated, operating voltage was decreased for all ranges of LiF thickness. By inserting a LiF thin layer with thickness of 5～10A, lower operating voltages and higher power efficiencies were achieved. For a thicker LiF layer, power efficiency was decreased rapidly for UV treated ITO because of insulating properties of LiF. On the other hand, for untreated ITO - higher hole injection barrier, it was kept relatively high value up to the range of 20A of due to the charge balance.