All-Solution-Processed Quantum-Dot Light-Emitting Diodes Based On Alcohol CuInS₂

Colloidal quantum dots?QDs?have advantage in terms of size-tunable emission wavelengths,solution processability,high quantum yield and color gamut,and have great application prospects in the display and lighting industry.Cu InS2 based QDs are low toxicity and low cost compared to the cadmium based counterparts.Their tunable emissions wavelengths with wide emission linewidths?>100nm?and large Stokes shifts make them candidate materials to achieve white LED and have great potential in the solid-state lighting.Recently,our group developed a simple in situ ligand exchange technology for the fabrication of 6-mercaptohexanol?MCH?capped CuInS₂ based QDs.After ligand exchange,the QDs can disperse in alcohol-based polar solvents such as methanol,ethanol and so on without changing their fluorescent properties.It is illustrated that the short-chain structure of MCH ligands and hydroxyl groups on the surface of QDs reducing the electron injection barrier,resulted in lower turn-on voltage,and enhanced the electron injection and charge transport rates at the interface,which greatly improve the device performance.Electroluminescent QD-LED devices based on the as-prepared CuInS2 QDs were fabricated through all-solution-process and optimized by finding the most appropriate charge transport materials and solvents for the alcohol-soluble QDs and regulating the film thickness of each layer.Finally a QD-LED device with lower turn-on voltage,high brightness and high current efficiency was obtained.The possibility of applying CuInS₂QDs in white QD-LED was also explored.The mainly achievements of this thesis are listed as follows:?1?Synthesis and Characterization of alcohol-soluble Cu InS₂ QDs.We preapared alcohol-soluble Cu InS₂ QDs powders with different emission wavelengths through in situ ligand exchange technology.Through comparative analysis,we confirm that the fluorescence characteristic of the new 6-MCH capped CuInS₂ based QDs have not changed.?2?Study on all-solution-processed QD-LED based on alcohol-soluble Cu InS2 QDs.We optimized the QD-LEDs by changing the electron transport materials?TIPD,ZnO,ZnMgO?possessing different LUMO energy levels and hole transport materials?Poly-TPD,TFB?possessing different hole transport speed.The devices showed materials best performance in all-color emission using ZnMgO and the mixture of Poly-TPD and TFB as electron and hole transport materials,respectively.And isopropyl alcohol is selected as the best solvent for fabrication CuInS₂ QDs thin films in the device assembling process.?3?Exploring the application of alcohol-soluble CuInS₂ QDs as emission materials in white QD-LED.We proved that our alcohol-soluble CuInS₂ QDs combined with AgInS₂ QDs or organic materials of thermally activated delayed fluorescence can serve as emission materials in all-solution-procesesd white QD-LED.