Light emitting efficiencies in organic light emitting diodes (OLEDs)

The interface between the organic layer and metallic anode of an OLED is crucial to the stability and the performance of the device. The α-septithiophene (α-7T) has been used as the buffer layer at the interface between the ITO electrode and the hole transport layer (HTL). The insertion of α-7T layer lowered the operating voltage and improved the external power efficiency. Moreover EL emission was not saturated up to 1600mA/cm 2 . The Maximum EL intensity was over 17000cd/m 2 and the maximum external power efficiency at 2000cd/m 2 is 6.41m/W and that at 100cd/m 2 is 9.341m/W. The EL intensity and external power efficiency of OLEDs depend on the thickness of the a-7T layer.