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Liao, Xiaojian ; Kahle, Frank-Julian ; Liu, Bin ; Bässler, Heinz ; Zhang, Xinghong ; Köhler, Anna ; Greiner, Andreas:
Polarized blue photoluminescence of mesoscopically ordered electrospun non-conjugated polyacrylonitrile nanofibers.
In: Materials Horizons.
Bd. 7
(2020)
Heft 6
.
- S. 1605-1612.
ISSN 2051-6355
DOI: https://doi.org/10.1039/D0MH00002G
Abstract
Conjugated polymers and oligomers that emit polarized light are used as active materials in various optoelectronic device applications, notably organic light-emitting diodes (OLEDs). Here, we demonstrate the fabrication of electrospun polarized light-emitting fibers from a non-conjugated polymer that can be aligned by a simple heat-stretching process. Upon excitation at 340 nm, ribbons made from the nanofibers show polarized deep blue luminescence with an anisotropy of 0.37 and a quantum yield of about 31%. Furthermore, they exhibit room temperature green phosphorescence with a lifetime of about 200 ms as well as a delayed deep blue fluorescence resulting from triplet–triplet annihilation (non-coherent photon upconversion) (TTA). Wide and small angle X-ray scattering experiments show that the stretched electrospun fibers are highly aligned with nearly perfect uniaxial orientation within the fabricated ribbons. This results in a mechanically robust and flexible material, with a high specific tensile strength (534 ± 28) MPa cm3 g−1 and toughness (79 ± 7) J g−1. The combination of efficient polarized deep blue luminescence, room temperature phosphorescence, TTA, mechanical robustness and flexibility of these fibers opens up new avenues for applications of non-conjugated polymers.