Dielectric permittivity of small-molecule matrices for organic optoelectronics: The key contribution of solid state molecular dynamics

Giavazzi, Davide; Painelli, Anna; Grisanti, Luca; D'Avino, Gabriele (2026) Dielectric permittivity of small-molecule matrices for organic optoelectronics: The key contribution of solid state molecular dynamics. Physical Review Materials, 10 (2). ISSN 2475-9953

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Abstract

The dielectric response of amorphous organic solids at the timescale of atomic motion has broad implications for their photophysics, governing spectroscopic properties and excited-state relaxation, among other phenomena. We present an original approach to the calculation of the vibrational contribution to the frequency-dependent calculations, and linear response theory, is applied to a set of amorphous carbazole-based small-molecule matrices, widely used as host materials in organic light-emitting diodes. Our analysis reveals the crucial role of hindered molecular rotations (librations) in the solid-state matrices of dipolar compounds. These modes manifest in the very-low frequency (<100 cm(-1)) region of the dielectric function, accounting for up to one-third of the total vibrational contribution to the static dielectric constant in a dipolar compound like 3,3'-di(carbazol-9-yl)5-cyano-1,1'-biphenyl. This low-frequency contribution is found to be crucial for determining the variations in the static dielectric constant across various materials.

Item Type:	Article
Uncontrolled Keywords:	amorphous organic solids; dielectric response; molecular librations
Subjects:	NATURAL SCIENCES > Physics
Divisions:	Division of Experimental Physics
Depositing User:	Ana Zečević
Date Deposited:	20 May 2026 12:07
URI:	https://fulir.irb.hr:/id/eprint/11990
DOI:	10.1103/fc1j-sp6w

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