Designing of low-cost, eco-friendly, and versatile photosensitive composites / inks based on carboxyl-terminated quantum dots and reactive prepolymers in a mixed solvent: Suppression of the coffee-ring strain and aggregation

Today, solution processable quantum dots (QDs) are receiving great attention as photon down converters for various photoluminescent device architectures such as next-generation solid-state lighting (SSL) and micro-light emitting diodes (LEDs). However, fabrication of QDs in commercial applications is still limited due to the lack of suitable QD composites that can address current technical issues such as polymer induced QD aggregation, ring-like deformation (called the coffee-ring effect), and so on. In the present study, carboxyl-terminated QD based composites are proposed as a potential solution. As a ligand molecule for model carboxyl-terminated QDs, 3-mercaptosuccinic acid (MSA) was used and MSA-capped QDs (MSA-QDs) showed excellent dispersion properties (up to 70%, by weight) in industrial solvents such as propylene glycol monomethyl ether (PGME) and propylene glycol monomethyl ether acetate (PGMEA). For photosensitive composites (e.g., photoresist, ink), photoreactive bisphenol A-based epoxy resins (e.g., SU-8) and cardo-based acrylic resins as binders are studied under co-solvent systems. As a result, the bisphenol A-based composite (e.g., SU-8/MSA-QD composites) were found to exhibit good QD uniformity in the matrix. In addition, corresponding resin-based QD inks are shown to significantly suppress ring-like deformation in droplets when cyclopentanone (CP) is used as co-solvent.