General Photo‐Patterning of Polyelectrolyte Thin Films via Efficient Ionic Bis(Fluorinated Phenyl Azide) Photo‐Crosslinkers and their Post‐Deposition Modification

Abstract

We have extended the well known bisfluorinated(phenyl azide) (bisFPA) methodology to develop an ionic bisFPA process suitable for photo‐crosslinking a wide variety of polyelectrolyte thin films. The crosslinking efficiencies (0.1–1.0 crosslink per photo‐reaction) are sufficiently high for the gel fraction to exceed 80 % for crosslinker concentrations of only a few weight %. This method is based on the photo‐induced formation of singlet nitrenes from FPAs and their insertion into unactivated C–H or other bonds, which thus general and not dependent on the presence of specific chemical functional groups. By derivatizing with ionic charge groups, we obtained ionic bisFPAs that can be properly dispersed into polyelectrolyte thin films. The sorbed moisture always present in these films however severely limits the photo‐crosslinking efficiency, apparently through nitrene protonation and intersystem crossing. This can be avoided by dehydration of the films, in some cases, to 130 °C for 10 min in nitrogen before photo‐exposure. We found that efficient photo‐crosslinking can then be achieved for polyelectrolytes even when they have nucleophilic groups. These include poly(styrenesulfonic acid) and their salts, poly(acrylic acid) and their salts, poly(dimethyldiallylammonium salts), as well as the electrically‐conducting poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonic acid) complex (PEDT:PSSH). We further demonstrate using this ionic bisFPA methodology both photo‐patterning and post‐deposition chemical modifications of polyelectrolyte thin films. This opens broad new possibilities in membrane, sensor and actuator technologies, as well as for organic semiconductor plastic electronics (such as field‐effect transistors) and polyelectrolyte‐based devices.

High internal quantum efficiency in fullerene solar cells based on crosslinked polymer donor networks

“…To crosslink the films, we used a recently developed steric-substituted bis(fluorinated phenyl azide; s -FPA) methodology1516. Its key advantage is the non-specificity that allows a wide variety of semiconductor polymers to be crosslinked at a sufficiently low crosslinker concentration that does not degrade their crucial semiconductor properties.…”

Efficient Conjugated‐Polymer Optoelectronic Devices Fabricated by Thin‐Film Transfer‐Printing Technique

“…For comparison, we also fabricated an identical bilayer structure using a UV cross-linker to cross-link the underlying TFB layer (20 nm) prior to spin-coating of the F8BT layer (80 nm), as described elsewhere. [30,31] Figure 2b compares the electroluminescence (EL) efficiency of the corresponding LEDs. All the devices exhibit sharp turn-on in both current and luminance at $2 V. Typically, F8BT:TFB blend films from xylene solution exhibit micronscale lateral phase separation as shown in the inset of Figure 2c.…”

“…The cross-linking occurs via a non-specific nitrene insertion into the alkyl and aromatic C-H bonds and therefore does not affect the primary conjugation of the polymers. Detailed processing steps are discussed elsewhere [30,31].…”

“…[23][24][25][26][27] To achieve multilayered conjugated-polymer structures, common strategies involve complex cross-linking and polymer synthetic routes to ensure that the solvent used for the subsequent layers is resistant to the preceding layer. [28][29][30][31] However, such methods are applicable to only a limited combination of materials as cross-linkers have to be chosen such that the effects on the electronic functionalities of the cross-linked materials are minimal. Transfer printing would eliminate the solvent-compatibility issues, but has to date only been used to transfer print electrodes or to laminate the final devices.…”

N‐2‐Aryl‐1,2,3‐triazoles: A Novel Class of UV/Blue‐Light‐Emitting Fluorophores with Tunable Optical Properties

“…[1] The last two decades evidenced the great advance in this research area, where fluorescent-active dyes have been applied to many different research fields, such as biological target imaging, [2] effective photosensors, [3] and novel photoactive materials. [4] Two key features of fluorescence-emitting molecules are quantum efficiency and the wavelengths of excitation and emission.…”