General bis(fluorophenyl azide) photo-crosslinkers for conjugated and non-conjugated polyelectrolytes

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2020-01, Vol.8 (1), p.253-261
• Main Authors: Teo, Desmond W. Y, Jamal, Zaini, Seah, Qiu-Jing, Png, Rui-Qi, Chua, Lay-Lay
• Format: Article
• Language: English
• Subjects: Conjugation; Crosslinking; Heterostructures; Morphology; Occlusion; Polyelectrolytes; Polymers; Thermal stability
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c9tc04060a

Crosslinking of semiconductors is critical towards building heterostructures to enable flexibility in the design of devices. Bis(fluorophenyl azide)s (FPAs) and their sterically-substituted derivatives (sFPAs) have been demonstrated to be able to photo-crosslink semiconductor polymers upon deep-UV exposure, stabilizing their morphologies in devices. Here, we report the development of both UV (254 nm) and i-line (365 nm) photo-activatable FPA and sFPA - FPA80 and sFPA82 - both incorporating 3,5-bis(methylene)-1,1-dimethyl-4-piperidonium, a conjugation-extending bridge that also bears an ionic group. These materials are useful for generic photo-crosslinking of both conjugated and non-conjugated polyelectrolytes. Good thermal stability and solubility in polar organic solvents are obtained. Good film retention (>80%) can be achieved with a crosslinker loading of less than 10 wt/wt% for high-molecular polymers ( M w > 100k), superior to alkyl bisazides. The photo-crosslinking efficiency of ca. 20% in model polyelectrolytes is limited by the occlusion of ionic crosslinkers from the polymer matrix where the C-H insertion reaction occurs, hence suppressing photo-crosslinking efficiency. Photo-patterning and crosslinking of polymer semiconductors, charge injection and/or transport layers are essential to improve the performance and/or functionality of organic semiconductor devices.