Acid–Base Reaction-Assisted Quantum Dot Patterning via Ligand Engineering and Photolithography

Abstract

The integration of quantum dots (QDs) into device arrays for highresolution display and imaging sensor systems remains a significant challenge in research and industry because of issues associated with the QD patterning process. It is difficult for conventional patterning processes such as stamping, inkjet printing, and photolithography to employ QDs and fabricate high-resolution patterns without degrading the properties of QDs. Here, we introduce a novel strategy for the QD patterning process by treating QDs with a bifunctional ligand for acid−base reaction-assisted photolithography. Bifunctional ligands, such as MPA (mercaptopropionic acid) or TGA (thioglycolic acid), have a carboxyl group on one side that allows the QDs to be etched along with the photoresist (PR) by the base developer, while on the opposite side the ligands have a thiol group that passivates the QD surface. Passivating MPA ligands on QDs facilitates patterning of QD films and makes them compatible with harsh photolithography processes. We successfully achieved the patterning of QDs down to 5 μm. We also fabricated high-resolution patterned QD light-emitting diodes (LEDs) and QD photodetector arrays. Our patterning process provides precise control for the fabrication of highly integrated QD-based optoelectronic devices.

Multi‐Interfacial Confined Assembly of Colloidal Quantum Dots Quasisuperlattice Microcavities for High‐Resolution Full‐Color Microlaser Arrays

“…To solve the above problems, surface modification on the initially assembled microrings seems to be a feasible method. [ 9,32 ] We directly immersed the CQD microring with oleic acid (OA) ligand in a methanol solution of mercaptopropionic acid (MPA) for a specific duration. Upon drying, SEM images revealed numerous cracks within the microring (Figure S18, Supporting Information).…”

Recent Advances and Challenges of Colloidal Quantum Dot Light‐Emitting Diodes for Display Applications

“…In 2022, J. H. Bae et al introduced a bifunctional ligandpassivated QD film that enabled acid-based reaction-assisted photolithography; the QD/PR layers could be simultaneously developed and stripped without an additional etching process. [190] Mercaptopropionic acid and thioglycolic acid were used as bifunctional ligands because of their carboxyl and thiol groups. The carboxyl group enables the QDs to be etched along with the PR by the base developer, and the thiol group passivates the QDs' surface to prevent any excessive performance deterioration.…”

Direct Photolithography Patterning of Quantum Dot‐Polymer

“…However, the incompatibility between photoresist and QDs, as well as the degradation of QD performance during etching, make it difficult to produce high-quality QD patterns. To improve this situation, several process improvements have been made, including adding interlayers between the photoresist layer and the QD layer, [42][43][44] functionalizing the ligands of QDs to reduce the impact of the photoresist, [45] and improving the photoresist material itself through modification. [46] Adding isolation layers (composed of polymers or other inorganic materials) can effectively block the mutual interference between the QD layer and the photoresist solvent.…”