Exciton Migration by Ultrafast Förster Transfer in Highly Doped Matrixes

Abstract

The energy transfer between dye molecules and the mobility of the corresponding excitons are investigated in polymethyl methacrylate films highly doped with perylene bisimide dyes. The dynamics is measured by group delay corrected, femtosecond broad-band spectroscopy revealing the transfer route via absorption changes that are specific for the participating species. In films doped with 0.14 M perylene orange an ultrafast homotransfer between the dye molecules is found by analyzing the loss of the excitation-induced anisotropy. The process exhibits a stretched exponential time dependence which is characteristic for Förster energy transfer between immobilized molecules. The transfer time is 1.5 ps for an average transfer distance of 2.3 nm and results in a high mobility of the optically generated excitons. In addition, we find that the excitons move to perylene orange dimers, which have formed in low concentration during the sample preparation. The observed energy transfer time is slightly shorter than expected for a direct Förster transfer and indicates that exciton migration by multistep transfer between the monomers speeds up the transport to the dimers. In samples doped with perylene orange and perylene red heterotransfer to perylene red takes place with transfer times down to 600 fs. The mechanism is Förster transfer as demonstrated by the agreement with calculations assuming electric dipole interaction between immobilized and statistically distributed donor and acceptor units. The model predicts the correct time dependence and concentration scaling for highly doped as well as diluted samples. The results show that ultrafast exciton migration between dye molecules in highly doped matrixes is an attractive and efficient mechanism to transport and collect energy in molecular systems and organic electronic devices. Further optimization should lead to a loss-free transport over distances typical for the thickness of active layers in these systems.

Solvent effects in the extraction and detection of polycyclic aromatic hydrocarbons from complex oils in complex environments

“…Interestingly, such energy transfer was less efficient in the methyl-β-cyclodextrin solutions, despite the fact that methyl-β-cyclodextrin was most efficient at extracting the two energy transfer partners into the aqueous environment. This result means that energy transfer efficiencies do not depend strictly on the concentration of the energy transfer partners (because the Me-β-cyclodextrin solution contains the highest amount of both donor and acceptor), a result that is in line with ample literature precedent [32][33][34][35]. There is also a strong possibility that the binding of one analyte affects the binding of a second analyte, either by promoting or disrupting that binding.…”

Energy transfer in pendant perylene diimide copolymers

“…This dye pair was chosen for the good spectral overlap between PO emission and PR excitation (SI Figure 1), which creates an efficient sensitiser and acceptor pair for FRET. 29,35 The calculated FRET radius of this pair is R 0 = 7 nm.…”

“…The polymer films reported in this paper have high concentrations of perylene units. While highly concentrated perylenedoped polymer films (1 − 3 M) have been prepared in previous work, 14,29,43 the majority of the literature reports perylene doped polymer films of 5 × 10 −4 − 5 × 10 −2 M 44,45 and weight percentages of 0.006 − 5%. 35,46,47,51 We present perylene films with concentrations in the range of 0.05-0.31M and 18-30 wt%.…”

“…[20][21][22][23][24][25][26][27] Accordingly the imide substituents can be used to control solubility and decrease aggregation without impacting the photophysical properties of the PDI chromophore. 28 Nevertheless, imide substituted perylenes still aggregate at FRET-enabling concentrations, 29 and thus aggregation remains a limiting factor inhibiting efficient FRET in PDI based LSCs.…”

Naphthacene-doped and undoped 5,12-naphthacenequinone crystals: Preparation, crystal structures and optical characteristics

“…In this paper, for the first time, we prepared 5,12-NpQ single crystal and high naphthacene (Np)-doped 5,12-NpQ crystal, a novel mixed crystal system, by crystallization from solution. Furthermore, the absorption, fluorescence spectra and transient photoluminescence (PL) decays of the above crystal systems have been investigated to probe into the optical characteristics of 5,12-NpQ with or without Np doping, which provided useful input for studying the interaction mechanism of the two components in organic mixed crystals [9][10][11][12].…”