Abstract
In this thesis, we focus on the fabrication and characteristics of light emission devices with nano-particles (NPs), including synthesis of nano-particles and their application of charge transporting layer and emission layer in optoelectronics. The fabrication processes were further optimized to improve the device efficiency. In the introduction, we briefly introduce the nano-particles for optoelectronics and their synthesis methods. In the second chapter, we introduce the operating principles and measurement methodology of organic light-emitting diodes (OLEDs). We review some light extraction methods of OLEDs and focus on the surface plasmonic effect. In a typical solution-processed OLED structure, we gained enhanced current density and luminance via doping gold nano-particles in hole injection layer, but the doping concentration of metal nano-particles was too low, leading to a trivial enhancement in device efficiency. In the third chapter, we utilized the chemical colloidal method, which has advantages of mass-production, reproducibility of products and low fabrication cost, to synthesize ZnO and TiO2 NPs. By optimizing chemical synthesis and thin film process parameters, organic photovoltaics (OPV) with ZnO NPs delivered a PCE of 8.7%. Perovskite solar cell with TiO2 NPs showed a PCE up to 13.2%. The excellent performance imply a promising potential of using metal-oxide NPs for optoelectronic application. In the fourth chapter, we integrated the home-made ZnO NPs and high quantum yield (QY) green CdSe@ZnS quantum dots (QDs) to fabricate quantum dot light-emitting diodes (QLEDs). Due to the roughness issue of ZnO NPs thin film, leakage current and unexpected blue emission were observed. Optimized device showed a current efficiency of 0.84 cd/A, a power efficacy of 0.28 lm/W, and an external quantum efficiency (EQE) of 0.34%. The CdZnSeS QDs with chemical composition gradient were further studied. Colloial CdZnSeS QDs were blended with Tris(4-carbazoyl-9-ylphenyl)amine (TCTA) as emission layer of the device. Vertical phase separation was observed between QDs and TCTA. The optimization of QLED via changing the QDs doping concentration and selecting the suitable electron transporting material 4,6-Bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine (B3PyMPM) was performed and the champion device showed a current efficiency of 31.5 cd/A, a power efficacy of 28.6 lm/W, and an EQE up to 7.5%. In the fifth chapter, we utilized a syringe pump and an automatically spray coater to synthesize colloidal perovskite QDs. Higher QY value of perovskite QDs (75.6%) was observed by utilizing our new method compared to traditional synthesis techniques. We also demostrated the preliminary results of QLED with colloidal perovskite QDs.