Photo-Cross-Linkable Polymer Inks for Solution-Based OLED Fabrication

Abstract

We introduce a catalyst-free, highly efficient, ambient temperature Diels−Alder reaction employing omethylbenzaldehyde derivatives as photocaged dienes as an ideal approach for forming three-dimensional insoluble networks for inkjet printing of OLED emissive layer. Herein, poly(methyl methacrylate) based polymers containing 4-(9H-carbazol-9-yl)-2-(3′-hydroxy-[1,1′-biphenyl]-3-yl)isoindoline-1,3-dione as a blue-green (λ max = 495−500 nm) thermally activated delayed fluorescence (TADF) emitter and a photochemically active maleimide/o-methylbenzaldehyde cross-linker couple were synthesized and their photo-cross-linking behavior was studied. Time resolved fluorescence measurements confirm that the TADF properties are maintained upon integration in a polymer network and HOMO/LUMO levels of the emitter species remain unchanged by the photo-cross-linking at 365 nm of the polymer chains. The network formation of the fluorescent films is evidenced by solvent resistance tests and monitored by Fourier transform infrared (FT-IR) spectroscopy as well as time of flight secondary ion mass spectroscopy (ToF-SIMS), showing the consumption of maleimide and o-methylbenzaldehyde groups with increasing irradiation time. The surface roughness is investigated via atomic force microscopy (AFM) and found to be unchanged by a solvent wash after the cross-linking. Furthermore, confirmation that the polymer solution can be printed on an inkjet-printer and subsequently photo-cross-linked for multilayer OLED device fabrication is obtained.

Organic light emitting diodes (OLEDs) with slot-die coated functional layers

“…For a multi-layer deposition, usually, non-orthogonal solvents are preferred; however, organic compounds have a similar chemical structure; therefore, it is challenging to find orthogonal solvents. Hence, there are many opportunities to develop crosslinkable materials 111,112 and/or solvent switching materials 64 , eliminating the need for orthogonal solvents.…”

A Universal In Situ Cross‐Linking Strategy Enables Orthogonal Processing of Full‐Color Organic Microlaser Arrays

“…For example, the utilization of orthogonal solvents enables the patterning of different organic materials on an identical substrate, while the damage issue in multiple processing cannot completely avoid. [ 27,28 ] Exploiting the cross‐linkable luminescent polymer to enhance solution stability allows the successive solution processing of multicolor light‐emitting devices; [ 5,29–32 ] unfortunately, the complicated chemical synthesis of these cross‐linkable functional materials significantly limits the material choice for full‐color microlasers. [ 33,34 ] Therefore, developing a robust approach that does not depend on chemical synthesis to integrate pixelated full‐color microlaser arrays is necessary for next‐generation flat‐panel laser displays.…”

Robust Scalable-Manufactured Smart Fabric Surfaces Based on Azobenzene-Containing Maleimide Copolymers for Rewritable Information Storage and Hydrogen Fluoride Visual Sensor

“…Mahdavian et al have incorporated the spiropyran chromophore into flexible acrylic copolymers for the preparation of dual-stimuli-responsive polyacrylic nanofibers via electrospinning, which can be used as smart platforms for reversible real-time data storage with enhanced photostability as well as improved response time by alternant acid/base vapors or UV/vis stimulations . Notably, maleimide and its derivatives have attracted great attention in developing stimulus-responsive material systems with simple molecular structures. − Through a simple synthetic strategy, such as the Diels–Alder reaction, a series of multi-stimuli-responsive polymer brushes or smart copolymers with tunable fluorescence properties have been fabricated. , Natural and synthetic polymers fabrics, such as cotton fabrics, as cost-effective three-dimensional scaffolds with various programmable surface functional modifications, have been extensively applied in oil/water separation, biomedicine, electrical device field, sensing, and artificial intelligence. − For instance, Zhu et al have fabricated smart Janus textile with adaptive moisture/thermal management by spray coating combined with in situ cross-linking of thermoresponsive moieties onto different sides of cotton fabric . Wang et al have reported simultaneous enhancement of stain removal and comfort control in cotton fabrics via surfaces decorated with cross-linked light and thermal dual-responsive copolymers .…”