Single‐Crystalline Optical Microcavities from Luminescent Dendrimers

• Published in: Angewandte Chemie International Edition Vol. 59; no. 31; pp. 12674 - 12679
• Main Authors: Iwai, Kohei, Yamagishi, Hiroshi, Herzberger, Colin, Sato, Yuji, Tsuji, Hayato, Albrecht, Ken, Yamamoto, Kimihisa, Sasaki, Fumio, Sato, Hiroyasu, Asaithambi, Aswin, Lorke, Axel, Yamamoto, Yohei
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 27.07.2020; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: Carbazole; Carbazoles; Chemistry; Chemistry, Multidisciplinary; Crystal morphology; Crystal structure; Crystallinity; Crystals; Dendrimers; Fragility; laser chemistry; light harvesting; Microcavities; Microcrystals; Organic compounds; photochemistry; Physical Sciences; Polarized light; Science & Technology; light harvesting; UP-CONVERSION; CARBAZOLE; dendrimers; photochemistry; laser chemistry; microcavities
• DOI: 10.1002/anie.202000712
• ISSN: 1433-7851

Microcrystallites are promising minute mirrorless laser sources. A variety of luminescent organic compounds have been exploited along this line, but dendrimers have been inapplicable owing to their fragility and extremely poor crystallinity. Now, a dendrimer family that overcomes these difficulties is presented. First‐, second‐, and third‐generation carbazole (Cz) dendrimers with a carbon‐bridged oligo(phenylenevinylene) (COPV2) core (GnCOPV2, n=1–3) assemble to form microcrystals. The COPV2 cores align uni/bidirectionally in the crystals while the Cz units in G2‐ and G3COPV2 align omnidirectionally. The dendrons work as light‐harvesting antennas that absorb non‐polarized light and transfer it to the COPV2 core, from which a polarized luminescence radiates. Furthermore, these crystals act as laser resonators, where the lasing thresholds are strongly coupled with the crystal morphology and the orientation of COPV2, which is in contrast with the conventional amorphous dendrimers. Carbon‐bridged oligo(phenylenevinylene) (COPV2)–carbazole core–shell dendrimers with molecular weight as large as 4600 g mol−1 form microcrystals in which dendrons and COPV2 work as light‐harvesting antenna and fluorophore, respectively. The microcrystals function as a laser resonator, where the light confinement mode tightly couples with the alignment of the dendrimers and the morphology of the crystals.