Determination of Traps' Density of State in OLEDs from Current–Voltage Analysis

A simple method to determine the traps' density of state (DOS) in organic light-emitting diodes (OLEDs) by manipulating the current–voltage (I–V) characteristic of the devices at room temperature is introduced. In particular, the trap-dependent space-charge limited current formula is simplified to obtain effective density of traps. In this study, poly(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo2,1,3 thiadiazol-4,8-diyl) (F8BT) and 2-Methoxy-5-(3',7'-dimethyloctyloxy) benzene-1,4-diacetonitrile (OC_1C_10-PPV) are selected as the OLEDs emissive layer. The trap DOS of F8BT- and OC_1C_10-PPV-based OLEDs are calculated in the magnitudes of 10^24 m^-3 and 10^23 m^-3, respectively. In addition, the results agree with the other conventional method which is used to determine the trap DOS in OLEDs. This calculation technique may serve as a robust and reliable approach to obtain the trap DOS in OLEDs at room temperature.