Self-assembly of a white-light emitting polymer with aggregation induced emission enhancement using simplified derivatives of tetraphenylethylene. Issue 34 (15th August 2016)

• Record Type: Journal Article
• Authors: Ravindran, Ezhakudiyan; Varathan, Elumalai; Subramanian, Venkatesan; Somanathan, Narayanasastri
• Is Part Of: Journal of materials chemistry. Volume 4:Issue 34(2016)
• Page Start: 8027
• Page End: 8040
• Publication Date: 2016-08-15
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c6tc02566h
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : Novel luminogen based copolymers exhibit bright white light emission with high quantum yield through aggregation induced emission enhancement due to J-aggregates. Abstract : White-light emitting materials and devices have gained a great deal of interest and play an important role in next generation solid-state lighting applications. The unique aggregation-induced emission (AIE) route offers a forthright solution to the bottleneck problem of aggregation caused quenching (ACQ) in the solid state. A significant fluorescence enhancement was realized by tailoring a new luminogen (2 Z, 2′ Z )-3, 3′-((9, 9-dihexyl-9 H -fluorene-2, 7-diyl)bis(3, 1-phenylene))bis(2-(4-bromophenyl)-3-phenylacrylonitrile) (FBPAN) based on the AIE strategy, which exhibits yellow fluorescence with a high quantum yield of 63.41%. Electroluminescence characteristics with a maximum luminance, current and power efficiency of 16673 cd m −2, 9.32 cd A −1 and 5.88 lm W −1, respectively, were obtained for FBPAN. The white light emitting polymers were obtained by the copolymerization of a 9, 9′-dihexylfluorene host with a FBPAN moiety as a covalent dopant. Bright white light emission with a high quantum yield of 80.2% was obtained from the copolymer FBPAN 0.5, which contained 0.5% FBPAN. Importantly, the copolymers exhibit enhanced emission upon aggregation, even at low compositions of FBPAN. A careful inspection reveals that the enhanced emission in the solid state is due to the formation of "J-aggregates" with ordered supramolecular self-assembly. Interestingly, the copolymer FBPAN 0.5 exhibits a unique ordered flower shaped self-assembly and significantly reduces the charge trapping due to balanced charge transport. As a result, bright and high efficiency white light emission was achieved with Commission Internationale de l'Eclairage (CIE) coordinates of (0.32, 0.31) and a maximum luminance, current and power efficiency of 13455 cd m −2, 7.56 cd A −1 and 5.32 lm W −1, respectively. The copolymers possess very low turn-on voltage in the range of 1.5 to 3 V.