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

Abstract

We report Stark fluorescence spectroscopy investigation of rubrene dispersed in a poly(methyl methacrylate) film. The features of the fluorescence spectrum are analogous to those in solutions. In the Stark fluorescence spectrum, the decrease of the fluorescence quantum yield in the presence of an external electric field is observed. This result shows that the yield of nonradiative decay processes is increased by the application of an external electric field. It is known that the fluorescence quantum yield for rubrene, which is nearly unity at room temperature, depends on temperature, and a major nonradiative decay process in photoexcited rubrene is ascribed to a thermally activated intersystem crossing (ISC). Equations that express the field-induced fluorescence quenching in terms of the molecular parameters are derived from the ensemble average of electric field effects on the activation energy of the reaction rate constant in random orientation systems. The molecular parameters are then extracted from the observed data. It is inferred that the field-induced increase in the yield of other intramolecular and intermolecular photophysical processes in addition to the ISC should be taken into account.

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

“…14 As described in Part II of the series of the papers, dominant bands in the fluorescence spectrum are also polarized along the Maxis. 17 In single crystals, much weaker absorption bands for which the polarization directions are not parallel to the M-axis also contribute to the spectrum in the wavenumber region higher than ∼20000 cm −1 . 14 This band having the different transition character is probably stemming from vibronic interaction with other electronic states.…”

“…SF spectroscopy investigation is presented in a companion paper. 17 II. EXPERIMENTAL METHODS Rubrene (Tokyo Chemical Industry, purified by sublimation) was used without further purification.…”

“…The change in the transition dipole moment in the presence of an external electric field is also characterized. SF spectroscopy investigation is presented in a companion paper …”

Influence of External Electric Fields on Photoluminescence and Charge Carrier Dynamics of π-Conjugated Polymer P3HT in Multilayer Films with Heterojunctions to TiO2 and Sb2S3

“…In the present results, however, the coefficient of the zeroth derivative component is extremely large, so the first and second derivative components could not be determined. The zeroth derivative component shows the change in PL intensity induced by the applied electric field (Δ I PL ) relative to the unperturbed PL intensity ( I PL ), thus giving information on the field-induced change in emission quantum yield. ,, Then, electric field effects on photoexcitation dynamics can be discussed, based on the zeroth derivative component of the E-PL spectrum.…”

“…The zeroth derivative component shows the change in PL intensity induced by the applied electric field (ΔI PL ) relative to the unperturbed PL intensity (I PL ), thus giving information on the field-induced change in emission quantum yield. 39,51,52 Then, electric field effects on photoexcitation dynamics can be discussed, based on the zeroth derivative component of the E-PL spectrum. E-PL spectra observed at the second harmonic of the modulation frequency of the applied AC voltage are shown in Figure 5.…”