Highly Ordered 2D-Assemblies of Phase-Segregated Block Molecules for Upconverted Linearly Polarized Emission

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Abstract

Materials based on the laminar ordering of self-assembled molecules have a unique potential for applications requiring efficient energy migration through densely packed chromophores. Here, employing molecular assemblies of coil–rod–coil block molecules for triplet–triplet annihilation upconversion (TTA-UC) based on triplet energy migration with linearly polarized emission is reported. By covalently attaching discrete-length oligodimethylsiloxane (oDMS) to 9,10-diphenylanthracene (DPA), highly ordered 2D crystalline DPA sheets separated by oDMS layers are obtained. Transparent films of this material doped with small amounts of triplet sensitizer PtII octaethylporphyrin show air-stable TTA-UC under non-coherent excitation. Upon annealing, an increase in TTA-UC up to two orders of magnitude is observed originating from both an improved molecular ordering of DPA and an increased dispersion of the sensitizer. The molecular alignment in millimeter-sized domains leads to upconverted linearly polarized emission without alignment layers. By using a novel technique, upconversion imaging microscopy, the TTA-UC intensity is spatially resolved on a micrometer scale to visually demonstrate the importance of molecular dispersion of sensitizer molecules for efficient TTA-UC. The reported results are promising for anti-counterfeiting and 3D night-vision applications, but also exemplify the potential of discrete oligodimethylsiloxane functionalized chromophores for highly aligned and densely packed molecular materials.

Original languageEnglish
Article number2004775
JournalAdvanced Materials
Volume32
Issue number48
Early online date29 Oct 2020
DOIs
Publication statusPublished - 3 Dec 2020

Keywords

  • 2D-assemblies
  • linearly polarized emission
  • photon upconversion
  • triplet energy migration
  • triplet–triplet annihilation

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