Issue 27, 2017

Understanding the molecular gelation processes of heteroatomic conjugated polymers for stable blue polymer light-emitting diodes

Abstract

Heteroatomic conjugated polymers (HCPs) can have complicated molecular structures with several heteroatoms in the repeat unit, which is helpful for designing color-tunable emitters, photovoltaic donors and high mobility materials. In order to understand their relatively complex molecular superstructure characteristics in depth, heteroatomic substitution-induced diverse non-covalent interactions must be investigated. Here, we systematically studied the gelation processing and its influence on the optoelectronic properties of a series of sp2 nitrogen (N) substituted polyfluorenes (PF8-co-DAF8) towards highly stable blue polymer light-emitting diodes (PLEDs). This heteroatomic substitution allows for diverse chain C–H⋯N hydrogen bonds, correlating with an excellent gelation behavior at room temperature. Films with a gelation superstructure show a weak interchain π–π interaction and energy transfer compared to non-gelation ones. PLEDs based on a gelation film give a stable, deep-blue emission with CIE coordinates of (0.16, 0.17) and a luminous efficiency (L.E.) of 1.30 cd A−1, while non-gelation film-based PLEDs display a stable, sky-blue emission (CIE: 0.20, 0.24; L.E.: 2.13 cd A−1). Diverse non-covalent interactions originating from the heteroatomic substitution cause a complicated molecular aggregation behavior in solution that can significantly affect the chain rearrangement in the film-casting process, thereby dominating the optoelectrical properties.

Graphical abstract: Understanding the molecular gelation processes of heteroatomic conjugated polymers for stable blue polymer light-emitting diodes

Supplementary files

Article information

Article type
Paper
Submitted
10 Apr 2017
Accepted
02 Jun 2017
First published
02 Jun 2017

J. Mater. Chem. C, 2017,5, 6762-6770

Understanding the molecular gelation processes of heteroatomic conjugated polymers for stable blue polymer light-emitting diodes

J. Lin, B. Liu, M. Yu, C. Ou, Z. Lei, F. Liu, X. Wang, L. Xie, W. Zhu, H. Ling, X. Zhang, P. N. Stavrinou, J. Wang, D. D. C. Bradley and W. Huang, J. Mater. Chem. C, 2017, 5, 6762 DOI: 10.1039/C7TC01541K

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