Electrode Modification Of Polymer Light Emitting Diodes

In recent years, polymer light emitting diodes (PLEDs) have been considered as apromising candidate for large area flat panel displays and solid state lighting due to theirunique advantages, such as low cost, light weight, easy solution processing, mechanicalflexibility, and so on. However, there are still many issues such as efficiency andstability need to be improved to realize high performance PLEDs.In this thesis, several electrode modification methods have been developed forPLEDs, and their device performance are investigated.1. The solution-processed graphene oxide (GO) as an efficient hole transport layer(HTL) is utilized to replace the PEDOT:PSS layer in PLED, with a configuration ofITO/GO/MEH-PPV/LiF/Al. In order to decrease the driving voltage of PLEDs usingGO as a HTL, ultraviolet-ozone (UVO) treatment was proposed to modify the interfacebetween GO and MEH-PPV. As determined by photoelectron spectroscopy andimpedance spectroscopy, an optimized UVO treatment results in a more favorableenergy level alignment and a decrease in series resistance.2. We study the effect of gold nanoparticles (Au NPs)-induced surface plasmons onthe performance of PLEDs with a configuration of ITO/GO/MEH-PPV/LiF/Al. Throughthe system experiments, we confirm that surface plasmon effect induced by Au NPs isnonfunctional in PLEDs with red emitting light, and the resons are investigated.3. The nanogratings are introduced into PLEDs by using soft nanoimprintinglithography. The light extraction from waveguide (WG) and surface plasmon polariton(SPP) modes is realized in PLEDs. As a result, the current efficiency is increased by35%when the gratings are patterned on both the PEDOT:PSS and MEH-PPV polymerlayers.