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.