Small molecule-based photocrosslinkable fluorescent materials toward multilayered and high-resolution emissive patterning

Abstract

Solution-processable green and red-emitting fluorophores possessing photopolymerizable acrylate units have been synthesized. Photocrosslinking was successfully performed in neat thin films at room temperature under low-dose UV irradiation at 365 nm. No further curing step was necessary to achieve insoluble emissive thin films displaying high optical quality. Up to 80% of the green emitting material processed as a non-doped thin film remained after photopolymerization. Despite competitive energy transfer occurring between the excited photoinitiator and the radiative excited state of red-emitting materials, up to 40% of the initial thickness could be achieved after development. The very low RMS roughness of the green and red photocrosslinked thin films after development (RMS < 0.7 nm) allowed us to fabricate multicolored stacks again with high optical quality (RMS roughness < 1.3 nm) after two cycles of irradiation and development involving successively red and green emitters. Resolved patterns as small as 600 nm in width could be obtained upon photolithography performed under an air atmosphere. High adhesion of the photocrosslinked materials on surfaces makes the resulting emissive thin films very promising for realizing complex emissive structures on flat or bend substrates as required in multiple applications such as optical data storage, organic lasers, organic light emitting diodes or counterfeiting.