Excited-State Dynamics of Polyfluorene Derivatives in Solution

Abstract

The excited-state dynamics of two polyfluorene copolymers, one fully conjugated containing phenylene vinylene units alternated with 9,9'-dihexylfluorenyl groups and the other segmented by -(CH2)8- spacer, were studied in dilute solution of different solvents using a picosecond single-photon timing technique. The excited-state dynamics of the segmented copolymer follows the Förster resonant energy-transfer model which describes intrachain energy-transfer kinetics among random oriented chromophores. Energy transfer is confirmed by analysis of fluorescence anisotropy relaxation with the measurement of a short decay component of about 60 ps. The fluorescence decay surface of the fully conjugated copolymer is biexponential with decay times of about 470 and 900 ps, ascribed to deactivation of chain moieties containing trans and cis isomers already in a photostationary condition. Thus, energy transfer is very fast due to the conjugated nature and rigid-rod-like structure of this copolymer chain.

Intrachain Energy Migration to Weak Charge-Transfer State in Polyfluorene End-Capped with Naphthalimide Derivative

“…Fluorescence depolarization is caused by transition dipole reorientation of the chromophores and has been a useful tool to probe energy migration in conjugated polymers. , It occurs due energy migration (and/or transfer) and conformational relaxation (torsion) of the chromophore segments. In our experiments, we see that the time-resolved fluorescence anisotropy relaxation of PF-BNI is very different from the PF anisotropy relaxation, as illustrated in Figure .…”

Synthesis and optical properties of a new triphenylamine-p-phenylenevinylene-small molecule with applications in high open-circuit voltage organic solar cells

“…The hole mobility of the new compound was also measured through hole-only defices and thin field-effect transistors (TFTs). Timeresolved fluorescence spectroscopy has been shown to be a useful tool for investigating many of the mechanisms involved in energy transfer processes in end-capped oligophenylene-vinylene oligomers, such as solvent relaxation and/or conformational relaxation of the conjugated backbone, 14 intrachain energy transfer in solutions, 15 or interchain energy transfer in solutions or films. 16 We chose to fabricate planar heterojunction OPVs, since for such architecture, the device operation is not dependent on the intricate morphology of the donor:acceptor blend as for BHJ cells, and therefore they are good prototypes for investigating the individual performance of the materials.…”

The effect of complexation with platinum in polyfluorene derivatives: A photo- and electro-luminescence study

“…Apart from the progress in understanding the relations among photo, optical and electrical properties with structure [8,9] and morphology [10], the relevant use of the fluorene moiety in photovoltaic cells has arisen due to its low lying HOMO level, which is a favorable feature for the open circuit voltage of such devices. The pioneering work of Andersson and Inganäs and co-workers [11][12][13] paved the way for other groups [14,15] to optimize polyfluorenes and demonstrate high device performance.…”