Correlation Between Charge Injection and Charge Balance in Organic Light Emitting Diodes Using LiF and IrO[subx] Interlayers.

We report the correlation between charge injection and charge balance using lithium fluoride/aluminum (LiP/Al) cathode and iridium oxide (lrOr)-coated indium tin oxide (ITO) anode in organic light emitting diodes (OLEDs). The turn-on voltage decreased from 6.7 to 1.0 V and luminous efficiency at 80 mA/cm[sup2] increased from 1.24 to 4.60 cd/A due to the presence of LiF and the high work function of IrO[subx]. When IrO[subx]. was used in the anode region, the luminous efficiency increment rate decreased from 40% in Al cathode OLED to 7% in LiF/Al cathode OLED. The value of the carrier density suggested that the majority carrier changed from electrons in ITO-LiF/Al OLEDs to holes in ITO/IrO[subx]-LiF/Al OLEDs, reducing the rate of increase. Therefore, it has been considered that charge injection should be increased and balanced in order to maximize the luminous efficiency. [ABSTRACT FROM AUTHOR]