Photoresist-guided indirect photopatterning of quantum dots via carbene-mediated ligand thermocrosslinking

Colloidal quantum dots (QDs) are leading candidates for next-generation optoelectronics owing to their tuneable bandgaps, narrow emission linewidths, and high luminescence quantum yields. For virtual-, augmented-, and mixed-reality display applications of these materials, patterning full-color QDs at μm-length scales is essential. However, existing photolithographic approaches often degrade QD luminance characteristics by exposing them to harsh processing conditions, or they compromise the structural fidelity of the resulting patterns. Here we report a photoresist-guided indirect (PIN) photopatterning strategy that includes (i) lithographic formation of sacrificial PR patterns, (ii) deposition of a crosslinked QD film on top, and (iii) PR stripping that removes the sacrificial PR, leaving behind crosslinked QD patterns on the substrate. QD crosslinking is mediated by a diazo-based ligand thermocrosslinker, Diazo-4-LiXer. Leveraging low-temperature (110-120 °C)-activated carbene chemistry, Diazo-4-LiXer bridges neighbouring QDs while maintaining their intrinsic photoluminescence and electroluminescence through repeated processing. Moreover, Diazo-4-LiXer enables thermocrosslinking without affecting the underlying photoresist pre-patterns, which serve as structural templates determining the thickness and fidelity of the QD patterns. Using PIN photopatterning, we realize high-fidelity RGB patterns exceeding 4,000 pixels per inch resolution and demonstrate integration-level scalability by fabricating a 10 × 10 passive-matrix full-colour RGB QD-LED array.