Fabrication of an all-spin-coated CdSe/ZnS quantum dot light-emitting diode

Abstract

Due to their unique technical properties, the importance of semiconductor nanocrystal quantum dots (QDs) increased over the last decades especially for the use of quantum dot light-emitting diodes (QD-LED) [1,2] or detectors [3]. In present QD-LED arrangements, layer stacks e.g. hole injection layer (HIL), hole transport layer (HTL), QD layer (QDL), hole blocking layer (HBL), and electron transport layer (ETL) are mostly formed by two or more process steps including spin-coating, thermal deposition or vapor deposition. The latter in general is used for assembling the ETL, because the QDs active matrix group (ligands) is unstable for organic solvents. Nevertheless a reduction of process steps and thus decreasing material consumption could be an advance in manufacturing QD-LEDs. Therefore we discuss the fabrication of an all-spin-coated CdSe/ZnS core shell type QD-LED only consisting of HIL, QDL, and ETL showing electroluminescence at 610 nm. Thereby the used ETL addition ally fulfils the function as HBL. Although the ETL has high electron mobility, the QD-LEDs conductivity was improved further through thermal annealing steps while fabrication

Freestanding High-Resolution Quantum Dot Color Converters with Small Pixel Sizes

“…For QDs encapsulated in organic ligands and monodispersed in solutions such as toluene, octane, or hexane, a controlled ligand exchange process is necessary for multilayer coatings . This process is time-consuming, especially as relatively thick films are required for near-complete absorption from the highly efficient blue LED emitters, resulting in films that are not chemically robust for post-processing steps. − QDs dispersed in an optically transparent curable polymer would not only result in chemical stability of the QD film but also protect the QDs from degradation due to ambient oxidation. ,,− Finally, to prevent the gradual loss in color intensity and short QD lifetime due to exposure to high photon fluxes and heat from the LED source, remote color converters placed away from the base converter and held at room temperature are a great alternative to achieve high-purity color profiles with a longer life cycle. − …”