Controlling Triplet-Harvesting Pathways and Nonlinear Optical Properties in Cu(I) Iodide-Based Polymers through Ligand Engineering

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Abstract
Organic-inorganic hybrid metal halides have become enormously important in optoelectronics, sensing, photosensitization, etc. In this study, we report a structural transition from a staircase configuration to a cubane configuration in Cu(I) iodide-based polymers influenced by the coordination behavior of two different π*-acceptor ligands. The staircase polymer structure, coordinated with 3-cyanopyridine, demonstrates efficient thermally activated delayed fluorescence from (metal+halide)-to-ligand charge transfer [1/3(M+X)LCT] states, with a singlet-triplet energy splitting of ∼9 meV. Conversely, upon replacement of the cyano with an amino group at the same position, a one-dimensional polymeric structure of Cu4I4 cubane-type clusters is formed, which shows strong cluster-centered (3CC) orange emission at room temperature. Temperature-dependent photoluminescence studies indicate that the 3CC state behaves as a self-trapped excitonic state with significant exciton-phonon coupling having a Huang-Rhys factor of 58.6. Additionally, we report this cubane-type cluster polymer acts as an efficient nonlinear optical material showing third harmonic generation with a χ(3) value of 1.32 × 10-18 m2 V-2 and a laser-induced damage threshold of 25.87 GW/cm2.
Funding Information
  • University Grants Commission
  • Department of Science and Technology, Ministry of Science and Technology, India (DST/NM/TUE/QM-10/2019 (C)/4)
  • Ministry of Education, India (MoE-STARS/STARS-2/2023-0313)
  • Indian Institute of Science Education and Research Pune

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