Solid state solvation: a fresh view

Year: 2023

Authors: Bardi B., Giavazzi D., Ferrari E., Iagatti A., Di Donato M., Phan Huu D. K. A., Di Maiolo F., Sissa C., Masino M., Lapini A., Painelli A.

Autors Affiliation: Univ Parma, Dept Chem Life Sci & Environm Sustainabil, Parco Area Sci 17-A, I-43124 Parma, Italy; Ist Nazl Ottica, CNR INO, Largo Fermi 6, I-50125 Florence, Italy; European Lab Nonlinear Spect, LENS, Via N Carrara 1, I-50019 Sesto Fiorentino, FI, Italy; ICCOM CNR, Via Madonna Piano 10, I-50019 Sesto Fiorentino, FI, Italy.

Abstract: The design of efficient organic electronic devices, including OLEDs, OPVs, luminescent solar concentrators, etc., relies on the optimization of relevant materials, often constituted by an active (functional) dye embedded in a matrix. Understanding solid state solvation (SSS), i.e. how the properties of the active dye are affected by the matrix, is therefore an issue of fundamental and technological relevance. Here an extensive experimental and theoretical investigation is presented shedding light on this, somewhat controversial, topic. The spectral properties of the dye at equilibrium, i.e. absorption and Raman spectra, are not affected by the matrix dynamics. Reliable estimates of the matrix polarity are then obtained from an analysis of the micro-Raman spectra of polar dyes. Specifically, to establish a reliable polarity scale, the spectra of DCM or NR dispersed in amorphous matrices are compared with the spectra of the same dyes in liquid solvents with known polarity. On the other hand, steady-state emission spectra obtained in solid matrices depend in a highly non-trivial way on the matrix polarity and its dynamics. An extensive experimental and theoretical analysis of the time-resolved emission spectra of NR in a very large time window (15 fs-15 ns) allows us to validate this dye as a good probe of the dielectric dynamics of the surrounding medium. We provide a first assessment of the relaxation dynamics of two matrices (mCBPCN and DPEPO) of interest for OLED application, unambiguously demonstrating that the matrix readjusts for at least 15 ns after the dye photoexcitation.

Journal/Review: MATERIALS HORIZONS

Volume: 10 (10)      Pages from: 4172  to: 4182

More Information: Work in Parma was funded by the PNRR MUR project ECS-00000033-ECOSISTER and benefited from the local HPC center and from the equipment and framework of the COMP-HUB and COMP-R Initiatives, funded by the Departments of Excellence program of the Italian Ministry for University and Research´ (MIUR, 2018-2022 and MUR, 2023-2027). Work in Florence was supported by the EU Horizon 2020 research and innovation program under grant agreement 871124 Laserlab-Europe. F. D. M.´s position was co-funded by the European Union – PON Research and Innovation 2014-2020. A. L. acknowledges support from the Fondazione Cassa di Risparmio di Torino (CRT), Visco3DCell project and from the University of Parma, MUR-DM737-2022-FIL-PROGETTI-A-LAPINI project.
KeyWords: Dynamics; Emission spectroscopy; Organic light emitting diodes (OLED); Raman scattering; Solvation
DOI: 10.1039/d3mh00988b

Citations: 8
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