Enhancing effects of nanoparticles on polymer-OLED performances

In an attempt to elucidate the influences of conductor Ag and semiconductor TiO₂ nanoparticles (NPs) onto device characteristics, the polymer organic light emitting diodes (P-OLEDs) with composite layers were prepared and investigated. The mentioned inorganic NPs were embedded into the hole transport layer [poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate); (PEDOT:PSS)] and into the emissive layer [poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene]; (MEH-PPV)], individually, with different concentrations. The fabrication of the P-OLEDs was achieved via solution processing. Complete device characteristics, namely, voltage-current, brightness, luminous efficiency, and electroluminescent spectrum were all determined and carefully analyzed to clarify the impacts on the device physics. Ag NPs synthesis was successfully carried out yielding approximately 6-nm diameter particle size. P-OLEDs fabricated using Ag/PEDOT:PSS and Ag/MEH-PPV nanocomposite layers exhibited enhancement in the device efficiency up to 45 %. Moreover, threshold and turn-on voltages were improved upon hybridisation of organic layers with TiO₂ nanoparticles. On the other hand, electroluminescent spectrum was not affected significantly by Ag NPs while TiO₂ shifted the dominant peak to the shorter wavelength.