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

Jin Yi Lin, Bin Liu, Meng Na Yu, Chang Jin Ou, Zhen Feng Lei, Feng Liu, Xu Hua Wang, Ling Hai Xie, Wen Sai Zhu, Hai Feng Ling, Xin Wen Zhang, Paul N. Stavrinou, Jian Pu Wang, Donal D.C. Bradley, Wei Huang

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

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.
Original languageEnglish (US)
JournalJournal of Materials Chemistry C
Volume5
Issue number27
DOIs
StatePublished - Jan 1 2017
Externally publishedYes

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