Emissive semi-interpenetrating polymer networks for ink-jet printed multilayer OLEDs

• Published in: Polymer chemistry Vol. 12; no. 39; pp. 5567 - 5573
• Main Authors: Kunz, Susanna V, Cole, Cameron M, Baumann, Thomas, Sonar, Prashant, Yambem, Soniya D, Blasco, Eva, Barner-Kowollik, Christopher, Blinco, James P
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 12.10.2021
• Subjects: Benzene; Copolymerization; Corrosion resistance; Crosslinking; Cycloaddition; Emissivity; Emitters; Fluorescence; Infrared spectroscopy; Inkjet printing; Interpenetrating networks; Multilayers; Organic light emitting diodes; Photoluminescence; Polymer blends; Polymer chemistry; Polymer films; Polymers; Prepolymers; Printers (data processing); Solvents
• ISSN: 1759-9954; 1759-9962
• DOI: 10.1039/d1py00794g

Solution-processing of multilayered Organic Light Emitting Diodes (OLEDs) remains a challenge that is often addressed by cross-linking polymer precursors into insoluble networks. Herein, we blend an emissive polymer carrying a Thermally Activated Delayed Fluorescence (TADF) emitter and a host species with a photo-cross-linkable polymer containing ortho -methylbenzaldehyde and maleimide groups as reactive cross-linkers to form a Semi-Interpenetrating Polymer Network (SIPN) upon irradiation at 365 nm. The progress of the cross-linking via Diels-Alder [4 + 2]-cycloaddition is monitored by FT-IR-spectroscopy and is correlated with the solvent resistance of the SIPN. Furthermore, the influence of the molecular weight and the cross-linker content on the efficiency of the cross-linking are investigated. The resulting polymer films show a high solvent resistance evidenced by photoluminescence and AFM measurements and are thus suitable for a successive solution-processed layer. Furthermore, a comonomer carrying the commercial host molecule 1,3-bis( N -carbazolyl)benzene (mCP) was synthesized in high yields, copolymerized and integrated in the emissive SIPN with good resistance against organic solvents. Lastly, the polymer blends were processed with an ink-jet printer and turned into an insoluble SIPN. Solution-processing of multi-layered Organic Light Emitting Diodes (OLEDs) remains challenging. Herein, we introduce a facile blending process of emitting polymers with photoreactive polymer strands, allowing for the generation of solvent resistant emissive layers.