Improvement of solution based conjugate polymer organic light emitting diode by ZnO–graphene quantum dots

In this paper conjugate polymer organic light emitting diode (OLED) device is improved by the insertion of electron transport layer of zinc oxide–graphene quantum dots (QDs). Prior to device fabrication, ZnO–graphene QDs thin film is thoroughly characterized by X-ray diffraction, X-ray photoelectron spectroscopy and field emission scanning electron microscopy. Aluminum is employed as the cathode of the device while ITO is used as the anode. Conjugate polymer layer of Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) and Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] are used as hole injection layer and emissive layer respectively. The device performance is analyzed by the current–voltage method. The hybrid OLED is showing four times higher current densities and improved turn on voltage of 2.5 V while the device without QD has turn on voltage of 3.5 V. Improvement of luminance is achieved by the insertion of QD layer at color coordinates of (0.56, 0.43).