This thesis presents a novel method for fabricating quantum dot light-emitting devices (QDLEDs)based on colloidal inorganic light-emitting nanoparticles incorporated into an organicsemiconductor matrix. CdSe core/ZnS shell nanoparticles were inkjet-printed in air andsandwiched between organic hole and electron transport layers to produce efficient photon-emissive media. The light-emitting devices fabricated here were tested as individual devices andintegrated into a display setting, thus endorsing the capability of this method as a manufacturingapproach for full-colour high-definition displays.
By choosing inkjet printing as a deposition method for quantum dots, several problemscurrently inevitable with alternative methods are addressed. First, inkjet printing promises simplepatterning due to its drop-on-demand concept, thus overruling a need for complicated andlaborious patterning methods. Secondly, manufacturing costs can be reduced significantly byintroducing this prudent fabrication step for very expensive nanoparticles.
Since there are no prior demonstrations of inkjet printing of electroluminescent quantum dotdevices in the literature, this work dives into the basics of inkjet printing of low-viscosity,relatively highly volatile quantum dot inks: piezo driver requirements, jetting parameters, fluiddynamics in the cartridge and on the surface, nanoparticle assembly in a wet droplet and packingof dots on the surface are main concerns in the experimental part. Device performance is likewisediscussed and plays an important role in this thesis. Several compositional QDLED structures aredescribed. In addition, different pixel geometries are discussed. The last part of this dissertationdeals with the principles of QDLED displays and their basic components: RGB pixels and organicthin-film transistor (OTFT) drivers. Work related to transistors is intertwined with QDLED work;ideas for surface treatments that enhance nanoparticle packing are carried over from self-assembled monolayer (SAM) studies in the OTFT field. Moreover, all the work done in this thesisproject was consolidated by one method, atomic force microscopy (AFM), which is discussedthroughout the entire thesis.
