Exciton diffusion, annihilation and their role in the charge carrier generation in fluorene based copolymers

Peckus, Domantas; Devižis, Andrius; Hertel, Dirk; Meerholz, Klaus; Gulbinas, Vidmantas

doi:10.1016/j.chemphys.2012.02.003

Cited by 27 publications

(23 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Many mechanisms for the generation of intrachain and interchain charges have been put forward based on detailed spectroscopy and photocurrent studies. Those include direct interband excitation of mobile electrons and holes (semiconductor model), [93][94][95]97,98 hot (vibrationally unrelaxed) exciton dissociation, 89,96 charge generation facilitated by exciton-exciton annihilation, 86,90,91,99 exciton splitting at impurities, 101 polaron-pair formation by sequential excitation, 91,92 and charge separation at amorphouscrystalline interfaces in P3HT. 87,88 A detailed discussion is beyond the scope of the present manuscript.…”

Section: 86-99mentioning

confidence: 99%

Sub-picosecond delocalization in the excited state of conjugated homopolymers and donor–acceptor copolymers

2013

View full text Add to dashboard Cite

In this feature article, we review and examine evidence that the primary photoexcited species in conjugated polymers is considerably delocalized. Localization occurs via a series of complex relaxation mechanisms on the <200 femtosecond time scale. We show that short-lived delocalization in the neutral excited state and charge separated state of bulk heterojunction blends might play an essential role in ensuring efficient formation of free charge carriers for photovoltaic applications. Finally, the additional parameter of intramolecular charge transfer character in the excited state of more recently developed donor-acceptor copolymers is discussed. Both delocalization and partial charge transfer reduce the binding of the electron and hole in photoexcited organic semiconductors and can help to overcome the bottleneck to macroscopic current generation in polymer solar cells.

show abstract

Section: 86-99mentioning

confidence: 99%

Sub-picosecond delocalization in the excited state of conjugated homopolymers and donor–acceptor copolymers

2013

View full text Add to dashboard Cite

show abstract

“…Various mechanisms for the generation of polarons in neat polythiophene or other conjugated polymer films have been suggested, including intrinsic free charge generation, 79 dissociation of excitons at defects, 80 at ordered/amorphous interfaces, 81 ultrafast hot exciton dissociation, 15 or excitonexciton annihilation. 82,83 For CPT, we can exclude annihilation based on the absence of any fluence-dependence in the TA dynamics and polaron yield (Fig. S12, ESI †).…”

mentioning

confidence: 99%

Salt-induced thermochromism of a conjugated polyelectrolyte

Peterhans

Alloa

Sheima

et al. 2017

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

We report here the photophysical properties of a water-soluble conjugated polythiophene with cationic side-chains. When dissolved in aqueous buffer solution (PBS, phosphate buffered saline), there is ordering of the polymer chains due to the presence of the salts, in contrast to pure water, where a random-coil conformation is adopted at room temperature. The ordering leads to a pronounced colour change of the solution (the absorption maximum shifts from 400 nm to 525 nm). Combining resonance Raman spectroscopy with density functional theory computations, we show a significant backbone planarization in the ordered phase. Moreover, the ratio of ordered phase to random-coil phase in PBS solution, as well as the extent of intermolecular interactions in the ordered phase, can be tuned by varying the temperature. Femtosecond transient absorption spectroscopy reveals that the excited-state behaviour of the polyelectrolyte is strongly affected by the degree of ordering. While triplet state formation is favoured in the random-coil chains, the ordered chains show a weak yield of polarons, related to interchain interactions. The investigated polyelectrolyte has been previously used as a biological DNA sensor, based on optical transduction when the conformation of the polyelectrolyte changes during assembly with the biomolecule. Therefore, our results, by correlating the photophysical properties of the polyelectrolyte to backbone and intermolecular conformation in a biologically relevant buffer, provide a significant step forward in understanding the mechanism of the biological sensing.

show abstract

“…The PL is collected at room temperature and under low excitation density ($100 mW/cm 2 ) to prevent photodegradation 37 and bimolecular effects. 38 The absorption spectrum of the fibers is comparable to that of the reference film, with almost identical positions of the main peaks, revealing a common origin of the optical transitions in both the systems. The main difference is a broadening of the fibers absorption spectrum at low energies.…”

mentioning

confidence: 69%

Enhanced emission efficiency in electrospun polyfluorene copolymer fibers

Morello¹,

Polini²,

Girardo³

et al. 2013

Applied Physics Letters

View full text Add to dashboard Cite

We report on the unique emission features of light-emitting fibers made of a prototype conjugated polymer, namely, poly [(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1 0 -3}-thiadiazole)] (F8BT), realized by electrospinning with diameters in the range of 500-1000 nm. The fibers display emission polarized along their axis, evidencing a favoured alignment of the polymer molecules. Emission efficiency and time resolved measurements reveal an enhancement of both the quantum efficiency and the radiative rate (up to 22.5%) of the fibers compared to spin-coated films, shedding more light on their potential as miniaturized photon sources in optoelectronic devices requiring high recombination rates. V C 2013 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4807894] Conjugated polymers have received a growing interest due to their high potential for application in many technological fields. They are intriguing materials on both the fundamental and application point of view. Till now, several applications have been implemented exploiting conjugated polymers as active media, including organic light-emitting diodes (OLEDs), 1 photovoltaic cells, 2 and field-effect transistors. 3 The photophysics of these materials has been investigated a lot in the last decade 4-8 in an attempt to rationalize the phenomena associated with charge and energy migration, especially in solid state samples, and to finally improve the performances of the developed devices. A distinctive feature of this class of polymers is the dependence of their optoelectronic properties on the peculiar micro/nanoscale structure and morphology. 9,10 For these reasons, most of the recent research has been dedicated to micro and nanostructured conjugated polymers, in which molecular backbones can be oriented and/or stretched along a preferential axis. [11][12][13][14][15] This orientation may induce changes in important physical properties and in their associated mechanisms, such as the charge transport, 16,17 photoluminescence (PL) anisotropy, 15,18-21 and energy transfer. 4,22 Among the micro and nanostructures made of conjugated polymers, electrospun fibers are rapidly emerging as quasi 1-dimensional (1-D) class of active nanomaterials. In these systems, the electric-field-induced stretching and the elongation of the polymer solution during the electrospinning process 23 are likely to favour a preferential alignment of the polymer backbones along the fiber longitudinal axis. Polarized Raman, infrared, and photoluminescence spectroscopies have evidenced such molecular alignment, 13,16,18,24 and ordered arrays of electrospun nanofibers made by conjugated polymers have been proposed as effective polarized light sources. 25 Importantly, the molecular packing in the stretched fiber structure can also affect the radiative rate, which is in turn sensitive to the dielectric tensor of the environment around the emitting chromophores, 26 to the coupling to vibrational modes, 27 to the molecular conformational properties, 28,29 and to variations of the conjugation length...

show abstract

Exciton diffusion, annihilation and their role in the charge carrier generation in fluorene based copolymers

Cited by 27 publications

References 22 publications

Sub-picosecond delocalization in the excited state of conjugated homopolymers and donor–acceptor copolymers

Sub-picosecond delocalization in the excited state of conjugated homopolymers and donor–acceptor copolymers

Salt-induced thermochromism of a conjugated polyelectrolyte

Enhanced emission efficiency in electrospun polyfluorene copolymer fibers

Contact Info

Product

Resources

About