Direct patterning of colloidal quantum dots with adaptable dual-ligand surface

Abstract

Colloidal quantum dots (QDs) stand at the forefront of a variety of photonic applications given their narrow spectral bandwidth and near-unity luminescence e ciency. Integrating desired forms of QD lms into photonic systems without compromising their optical or transport characteristics is the key to bridging the gap between expectations and outcomes. Here, we devise a dual-ligand passivation system comprising photocrosslinkable ligands and dispersing ligands to enable QDs to be universally compatible with solution-based patterning techniques. The successful control on the structure of both ligands allows multiscale, direct patterning of the dual-ligand QDs on various substrates via commercialized photolithography (i-line) or inkjet printing systems without compromising the optical properties of QDs or the optoelectronic performances of the devices implementing them. Our approach offers a versatile way of creating various structures of luminescent QDs in a cost-effective and non-destructive manner, and thus enables the implementation of QDs in a range of photonic applications. MainColloidal quantum dots (QDs) are promising materials for use in next-generation light sources due to their wide-ranging bandgap tunability, narrow spectral bandwidths, and near-unity luminescence quantum yields (QY) [1][2][3][4][5] . Together with the capability of cost-effective solution processing, QDs have become the key light-emissive materials for information displays 3,5−7 . The patterned QD down-conversion layer on blue light-emitting diodes (LEDs) renders high-color reproduction and ultra-high image quality in full-color displays 8,9 . Likewise, a laterally patterned array consisting of red, green, and blue (RGB) QD-LEDs, in which QDs convert electrically pumped charge carriers into photons, allows for excellent color gamut and brightness as well as light-weight, thin, and exible form factors [10][11][12][13] , which are suited for wearable neareye displays for virtual reality (VR) and augmented reality (AR) devices. For these "mixed-reality" applications, the QD deposition process should enable the patterning of RGB QDs (or RG QDs along with the bank) into a few micrometer sub-pixels over a large area with high-precision and high-delity 14,15 . At the same time, the process should not disrupt the optical and transport characteristics of QDs and adjacent functional layers. Moreover, from a practical standpoint, it poses great bene t if one can use equipment that are already deployed in display device manufacturing steps for the patterning process.

Surface passivation of intensely luminescent all-inorganic nanocrystals and their direct optical patterning

“…We showed that after systematic surface property engineering, ILANs were suitable for various industrially adapted patterning techniques, including direct optical lithography of functional inorganic nanomaterials (DOLFIN) 19,20 and inkjet printing, to design luminescent microscale structures with a spatial resolution down to 2 μm and a line edge roughness of 200 nm. Recently, many NC patterning strategies have been used to fabricate QLEDs with high performance [21][22][23] . The ability to reliably obtain ILANs along with the development of various material-adapted patterning techniques creates a versatile platform for next-generation QD-based optoelectronic devices.…”

Impact of Morphological Inhomogeneity on Excitonic States in Highly Mismatched Alloy ZnSe1–XTeX Nanocrystals

“…Semiconductor alloying is an effective and versatile tool for customizing the intrinsic physical properties of materials such as the bulk bandgap, effective mass of charge carriers, and lattice parameter on demand. Reducing the dimension of semiconductor alloys to the nanoscale permits additional control of the distribution of charge carriers and their dynamics, which enables us to achieve almost arbitrary control of optical and electrical characteristics of materials. − Nanocrystals (NCs) made of semiconductor alloys, whose physical dimensions allow for efficient charge carrier recombination and cost-effective solution processing, have attracted considerable attention as next-generation photon emitters in a wide range of applications, including tunable lasers, − light-emitting diodes, − and luminescent solar concentrators. − …”

Progress in the Development of Active-Matrix Quantum-Dot Light-Emitting Diodes Driven by Non-Si Thin-Film Transistors

“…Although full-color, high-resolution QLEDs could be demonstrated based on photolithography, the procedure to minimize the damages is exceedingly complicated [ 142 , 143 ]. Recently, a direct QD patterning method has been reported, which is a technique for patterning QDs based on photolithography but without the PR processes [ 131 , 144 , 145 , 146 , 147 , 148 ]. It can be achieved by adopting light-responsive ligands onto the surface of QDs, which chemically binds QDs upon illumination to firmly hold the pattern against the following wash-out step.…”

“…UV exposure to the modified QD film induces a chemical reaction between azides and the alkyl chain of QD ligands, resulting in a crosslinked QD layer, as shown in Figure 5 c. Full-color, high-resolution QD patterns of >1400 PPI were demonstrated, and red crosslinked QLEDs exhibited an EQE of 14.6%. In 2022, Hahm et al proposed direct patterning with dual ligands composed of dispersing ligands and photo-cross-linkable ligands to maintain the PL QY during photo-crosslinking [ 148 ]. As a result, they successfully demonstrated full-color QLED arrays employing the patterned QD films in a high resolution of >15000 PPI without a performance loss.…”