Electrical and electroluminescence properties of ITO/PEDOT:PSS/TPD:Alq3:C60/Al organic light emitting diodes

Organic light emitting diodes (OLEDs) of ITO/PEDOT:PSS/TPD:Alq3:C60/Al with different C60 concentrations (0–6.0 wt.%) have been fabricated. The physical parameters including electrical and optical properties of the samples have been measured by Luminance–current–voltage (L–I–V) characteristics and optical absorbance. The current–voltage characteristics indicate that field-emission tunneling injection dominates in the diodes at high applied voltages. It is found that with increasing the concentration of C60, the injection barrier for holes slightly reduces and the hole’s mobility increases over two orders of magnitude. Also, electroluminescence enhances with the presence of C60 in the blend; optimum current efficiency occurs at 3 wt% C60. The method provides a simple way of increasing the efficiency of OLEDs.