The current density-voltage (J-V) characteristics of organic light-emitting devices (OLED) having buffer layers based on the WKB approximation of the tunneling model were investigated. The turn-on voltage of the device was lowered by the insertion of an insulating buffer layer of proper thickness. Good buffer layer for electron injection was observed to have high resistivity and a low conduction band minimum (CBM) level. It was found that the quantitative estimation of the optimal buffer layer thickness was related to the thickness of the organic layer.
