Nondestructive Photopatterning of Heavy‐Metal‐Free Quantum Dots

Abstract

Electroluminescence from quantum dots (QDs) is a suitable photon source for futuristic displays offering hyper‐realistic images with free‐form factors. Accordingly, a nondestructive and scalable process capable of rendering multicolored QD patterns on a scale of several micrometers needs to be established. Here, nondestructive direct photopatterning for heavy‐metal‐free QDs is reported using branched light‐driven ligand crosslinkers (LiXers) containing multiple azide units. The branched LiXers effectively interlock QD films via photo‐crosslinking native aliphatic QD surface ligands without compromising the intrinsic optoelectronic properties of QDs. Using branched LiXers with six sterically engineered azide units, RGB QD patterns are achieved on the micrometer scale. The photo‐crosslinking process does not affect the photoluminescence and electroluminescence characteristics of QDs and extends the device lifetime. This nondestructive method can be readily adapted to industrial processes and make an immediate impact on display technologies, as it uses widely available photolithography facilities and high‐quality heavy‐metal‐free QDs with aliphatic ligands.

Direct photocatalytic patterning of colloidal emissive nanomaterials

“…In direct optical lithography, patterns are formed by photoinduced chemical reactions of photosensitive ligands or additives, which result in a solubility change of nanomaterials [e.g., metal oxide (16), PeNCs (17), and QDs (12)] at light-exposed regions without the need for a polymeric photoresist. Various photosensitive motifs and photochemical reactions such as azide (17)(18)(19)(20)(21), benzophenone (22), cinnamoyl (23), photo-acid generation (12), oxime sulfonate (13), thiol-ene (24)(25)(26)(27), photo-amine generation (28), oxide bridging (16), photo-oxidation (29), and alkene cross-linking (30) have been explored for direct optical patterning of colloidal emissive nanocrystals. However, the lithography process often induces substantial surface damage to the deposited emissive nanomaterials, thereby degrading their optical properties such as PLQY (13,17).…”

Direct Photo-Patterning of Efficient and Stable Quantum Dot Light-Emitting Diodes via Light-Triggered, Carbocation-Enabled Ligand Stripping

“…Patterned QLEDs show EQEs (up to ∼14.7% for red QLEDs) that are much lower than the best individual (or nonpatterned) devices. (ii) Direct photopatterning methods via designed surface photochemistry ,− are built on two core concepts of QDs: namely, the surface chemistry and colloidal stability, and enable photolithographic patterning of QDs in the absence of traditional photoresists. Despite the impressive versatility, the ligand photochemistry involved in direct photopatterning, mostly on the basis of photodecomposable ligands or photo-cross-linkers, profoundly affects the photophysical properties of patterned QDs via various factors, including radicals and surface traps .…”

High-Resolution Multicolor Patterning of InP Quantum Dot Films by Atomic Layer Deposition of ZnO

“…25−29 Typical photopatterning of QD films involves the use of photosensitive and cross-linkable ligands or additives to provide solvent resistance to the QD areas exposed to light. 30,31 However, QD and photosensitive organic molecule mixtures inevitably reduce the colorconversion efficiency of QD color filters and charge injection in light-emitting diode (LED) devices. Additionally, the typical method is limited to a certain QD film thickness, owing to the limited penetration depth of UV light in the QD film.…”

“…The inkjet printing method is currently used for QD pixel formation; however, high-resolution patterning for augmented and virtual reality (AR/VR) applications (>1000 PPI) is limited owing to the physical size of the ink droplet. − Additionally, nozzle clogging and the coffee ring effect are fundamental limitations. Although transfer printing and electrohydrodynamic jet printing can provide relatively high-resolution QD patterns, − optical lithography is an ideal method for patterning high-resolution QD patterns, − considering that this technique is well established in the semiconductor industry. − Typical photopatterning of QD films involves the use of photosensitive and cross-linkable ligands or additives to provide solvent resistance to the QD areas exposed to light. , However, QD and photosensitive organic molecule mixtures inevitably reduce the color-conversion efficiency of QD color filters and charge injection in light-emitting diode (LED) devices. Additionally, the typical method is limited to a certain QD film thickness, owing to the limited penetration depth of UV light in the QD film …”