Hybrid Light‐Emitting Diodes from Microcontact‐Printing Double‐Transfer of Colloidal Semiconductor CdSe/ZnS Quantum Dots onto Organic Layers

Abstract

Colloidal semiconductor nanocrystals have been attracting increasing technological interest for applications in lighting and flat-panel display applications. [1][2][3][4][5][6][7] In particular, continuing improvements in synthetic methods have enabled the design of high-quality quantum dot (QD) structures with photoluminescence (PL) ranging across the visible spectrum, a PL full width at half maximum (FWHM) less than 30 nm, and a PL efficiency higher than 50%.

Flexible quantum dot light-emitting diodes for next-generation displays

“…In case of the head-mount displays or virtual-reality displays, where flexible displays can be applied, implementation of even higher resolution displays is required to project three-dimensional synaptic images by magnifying the original two-dimensional images. There are two major approaches to patterning and integrating differently colored QDs with high resolutions onto the display paneltransfer printing 100 and inkjet printing. 101 Since the as-synthesized colloidal QDs are dispersed in a solution phase, the spin-casting process was typically used in the early QLED studies, which led to monochromatic light-emitting devices.…”

Microcontact Printing: Limitations and Achievements

“…Gigli and coworkers used drop-casting of colloidal semiconductor quantum dots on glass with controlled evaporation of the solvent, which allowed the self-assembly of the nanocrystals into large-area periodic structures. [140] Conformal contact of a PDMS stamp with the nanocrystal film was sufficient to ink the stamp and transfer the ordered quantum-dot layer onto small-molecule organic layers. Wolf and coworkers moved the meniscus of a colloidal suspension over a patterned layer to self-assemble particles with high precision inside the features.…”

Characterization of Quantum Dot/Conducting Polymer Hybrid Films and Their Application to Light‐Emitting Diodes

“…Previously, several approaches have been taken in order to prevent such possible damage to organic underlayers during the QD emission layer deposition: processing with a mixed solution of QD and organic matrix material, [8][9][10][11][12] the introduction of robust matrix layers (i.e., a cross-linkable or robust conjugated polymer [13][14][15] or metal oxide inorganic layer [16,17] ), or pattern transfer techniques (i.e. micro-contact printing of QDs [19] ). These approaches can produce uniform QD layers on the basis of the spin-coating method, but they are difficult to apply to other solution-based processes, such as drop-casting or roll-coating methods, which are inevitably required for the fabrication of large-area devices in large quantities, mainly due to the constraints from either massive aggregation of QDs during the processing or additional requirements of intricate and expensive procedures (such as sputtering or thermal annealing).…”