Dresden 2020 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 28: Focus: Exploitation of Anisotropy in Organic Semiconductors I (joint session CPP/HL)

HL 28.7: Talk

Tuesday, March 17, 2020, 12:15–12:30, ZEU 222

Polarized blue photoluminescence of mesoscopically ordered electrospun non-conjugated polyacrylonitrile nanofibers — Xiaojian Liao¹, •Frank-Julian Kahle², Bin Liu^3,4, Heinz Bässler², Xinghong Zhang³, Seema Agarwal¹, Anna Köhler², and Andreas Greiner¹ — ¹Macromolecular Chemistry II, U Bayreuth, Germany — ²Softmatter Optoelectronics, U Bayreuth, Germany — ³MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Zhejiang University, P. R. China — ⁴School of Energy and Power Engineering, North University of China, China

We demonstrate the fabrication of electrospun fibers from the non-conjugated polymer polyacrylonitrile (PAN) that can be aligned by a simple heat-stretching process. Upon excitation at 340 nm ribbons made from the nanofibres show polarized deep blue luminescence with an anisotropy of 0.37 and a quantum yield of about 0.31. Furthermore, they exhibit room temperature green phosphorescences with a lifetime of about 200 ms as well as a delayed deep blue fluorescence resulting from triplet-triplet annihilation (non-coherent photon upconversion). Wide and small angle X-ray scattering experiments show that the stretched electrospun nanofibers are highly aligned with nearly perfect uniaxial orientation within the fabricated ribbons. This results in mechanical robustness and flexibility, with a high specific tensile strength (534 ± 28) MPa· cm³/g and toughness (79 ± 7) J/g. 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.