Ligand‐Crosslinking Strategy for Efficient Quantum Dot Light‐Emitting Diodes via Thiol‐Ene Click Chemistry

Abstract

While solution‐processable colloidal quantum dots (QDs) offer cost‐effective and large‐scale manufacturing, they can be susceptible to subsequent solution processes, making continuous processing challenging. To enable complex and integrated device architectures, robust QD films with subsequent patterning are necessary. Here, we report a facile ligand‐crosslinking strategy based on thiol‐ene click chemistry. Thiol molecules added to QD films react with UV light to form radicals that crosslink with QD ligands containing carbon double bonds, enabling microscale photo‐patterning of QD films and enhancing their solvent resistance. This strategy can also be extended to other ligand‐capped nanocrystals. It is found that the swelling of QD films during the process of binding with the thiol molecules placed between the ligands contributes to the improvement of photoluminescence and electroluminescence properties. These results suggest that the thiol‐ene crosslinking modifies the optoelectronic properties and enables direct optical patterning, expanding the potential applications of QDs.

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).…”

Cross-linking strategies for hole transport/emissive layers in quantum-dot light-emitting diodes

“…6(f)). 60 The formed robust cross-linked QD film exhibited insensitivity to oxygen or water. Furthermore, using the crosslinked InP QDs as the emissive layer, their QD-LED showed a peak CE of 23.04 cd A À1 , which was even 158% higher than that of their conventional counterpart.…”

A Photoinitiator-Grafted Photoresist for Direct In Situ Lithography of Perovskite Quantum Dots

“…Direct optical lithography, a method in which QDs are patterned directly by the light-induced change in solubility, is considered to be an effective patterning technique that can produce definition patterns over large areas on desired substrates . Several approaches based on different photochemical mechanisms have been proposed, such as polarity change, unsaturated double bond cross-linking, thiol–ene, , azide, or benzophenone cross-linking, and so on. Talapin et al developed a general strategy by modifying the colloidal solubility of QDs through chemical transformation of photoactive ligands on the surface of QDs. , A different strategy, is to use photoactive additives containing azide groups as a promising “linking agent” to cross-link the native surface ligands under UV irradiation .…”