Stark Spectroscopy of Rubrene. I. Electroabsorption Spectroscopy and Molecular Parameters

Abstract

Electroabsorption spectroscopy investigation and the determination of molecular parameters for rubrene dispersed in a poly(methyl methacrylate) (PMMA) matrix are reported. The features of the band system in the absorption spectrum in PMMA are analogous to those in solutions. The changes in the electric dipole moment and the polarizability between the excited and ground states are determined from analysis of the Stark effect in the absorption band. The change in the transition dipole moment in the presence of an external electric field is also observed. Although rubrene is predicted to be classified as a nonpolar molecule, there is a contribution of the difference in the electric dipole moment between the excited and ground states to the electroabsorption spectrum. The origin of the nonzero difference in the electric dipole moment is argued. Stark fluorescence spectroscopy investigation is reported in Part II of this series.

Stark Spectroscopy of Rubrene. II. Stark Fluorescence Spectroscopy and Fluorescence Quenching Induced by an External Electric Field

“…This result would advocate the interpretation of the EA spectra presented in Part I. 11 The three fluorescence spectra are also similar to each other, although the rubrene/PMMA film containing 0.2 mol % rubrene shows a slight blueshift. The absorption and emission spectra for single crystals and an amorphous film of rubrene have been reported by Irkhin et al 14 They obtained the intrinsic spectra by eliminating experimental artifacts such as reabsorption effect.…”

“…The method of sample preparation has already been described in Part I. 11 The sample substrate has the layered structure of quartz/ITO/(rubrene/PMMA)/aluminum, where ITO denotes the indium tin oxide film, and rubrene/PMMA represents a poly(methyl methacrylate) film in which rubrene is dispersed. The sample was prepared by using spin-coating technique, and the benzene solution containing ∼3% by mass PMMA and ∼3 mM rubrene was used, unless otherwise noted.…”

“…However, we can determine a few molecular parameters from the experiments using unpolarized light. The coefficient B φ ′ is given by an expression that is similar to eq 4 in Part I for the EA spectrum, 11 and it is related to the difference in the polarizability:…”

“…If molecules are immobilized and the change in absorbance induced by F is negligible at the wavelength of photoexcitation, the coefficient A φ ′ should originate from the field-induced change in fluorescence quantum yield and the field-induced change in transition dipole moment. 11 Both of these contributions are independent of the angle φ, and thus the discussion of them in the SF spectroscopy using unpolarized light is rationalized. The fieldinduced change in the fluorescence quantum yield can be ascribed either to the field effects on radiative and/or nonradiative rate constants or to the field-induced change in the population of the fluorescent state.…”

Hybrid Loss‐Compensated Plasmonic Device

“…The PL emission involves a weak peak at the wavelength of 470 nm which is related to the emission of PMMA layer and also the PL emission of EY51 thin film on PMMA layer shows a blue shift rather than pristine Rubrene on the glass substrate due to the formation of some aggregations at the interface of molecules . The result of Rubrene‐like molecule–light interaction in the hybrid plasmonic microcavity promises novel opportunity to study modifiying molecular bonding and chemical landscape in next research works …”