Well‐Defined and Monodisperse Linear and Star‐Shaped Quaterfluorene‐DPP Molecules: the Significance of Conjugation and Dimensionality

Kanibolotsky, Alexander L.; Vilela, Filipe; Forgie, John C.; Elmasly, Saadeldin E. T.; Skabara, Peter J.; Zhang, Kai A. I.; Tieke, Bernd; McGurk, John; Belton, C.; Stavrinou, Paul N.; Bradley, Donal D. C.

doi:10.1002/adma.201100308

Cited by 50 publications

(44 citation statements)

References 36 publications

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“…S1 †). In comparison to other T4 compounds, 20 where there was no uorescence or ECL observed above 450 nm, for T4BT-B there was luminescence observed even above 550 nm, which can be related to the addition of BT units, attributing to longer wavelength emission. However, the ECL monitored is total light produced rather than monitoring a specic wavelength.…”

Section: Electrochemiluminescence Propertiesmentioning

confidence: 79%

Novel electrochemiluminescent materials for sensor applications

et al. 2014

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Electrochemiluminescence (ECL) uses redox reactions to generate light at an electrode surface, and is gaining increasing attention for biosensor development due to its high sensitivity and excellent signal-to-noise ratio. ECL studies of monodisperse oligofluorene-truxenes (T4 series) have been reported previously, showing the production of stable radical cations and radical anions, generating blue ECL. The compound in this study differs from the original structures, in that there are 2,1,3-benzothiadazole (BT) units inserted between the first and second fluorene units of the quarterfluorenyl arms. It was therefore anticipated that the incorporation of these highly luminescent and ECL-active compounds into sensor development would lead to significant decreases in detection limits. In this contribution, we report on the impact of incorporating these novel complexes into sensor devices on the ECL efficiency, as well as the ability of these to improve the detection sensitivity and decrease the limit of detection using the reagent-free detection of model analytes. The real world impact of these compounds is elucidated through the comparison with more standard ECL materials such as ruthenium-based compounds. The potential for multiple applications is to be examined within this contribution.

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Section: Electrochemiluminescence Propertiesmentioning

confidence: 79%

Novel electrochemiluminescent materials for sensor applications

et al. 2014

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“…7 The two absorption bands observed for DPP-based donor-acceptor molecules are well-known and the high and low energy bands have previosuly been assigned to a π-π* transition of the conjugated donor unit and a transition of the DPP unit respectively. 17,25 This model implies a transition between an occupied molecular orbital and an unoccupied one where one or both shows some degree of localisation on part of the molecule, however, published DFT calculations for DPP-copolymers appear to conflict with this understanding suggesting rather that both the frontier molecular orbitals have a similar degree localisation centred on the DPP unit. This behaviour has led to the low energy optical transition being described as an intramolecular charge transfer (ICT) from the donor to the acceptor unit, in line with the model proposed for other donor-acceptor copolymers.…”

Section: Resonant Raman Spectroscopymentioning

confidence: 99%

“…[1][2][3][4][5][6] Particularly for photovoltaic applications, the low energy gaps of donor-acceptor copolymers are attractive since they can be tuned to optimise harvesting of the solar emission spectrum. 5,10,[14][15][16][17] The high photovoltaic performance of D-A copolymers has been attributed in part to effective charge carrier transport, [18][19][20] but particularly to efficient charge photogeneration related to the charge transfer character of the longest-wavelength electronic transitions. 1,[9][10][11][12][13] One particularly interesting electron-accepting unit is diketopyrrolopyrrole (DPP), which is highly electron-deficient and so can provide very low energy gap materials when combined with an electron rich donor unit such as thiophene or its derivatives.…”

Section: Introductionmentioning

confidence: 99%

Natures of optical absorption transitions and excitation energy dependent photostability of diketopyrrolopyrrole (DPP)-based photovoltaic copolymers

Wood

Wade

Shahid

et al. 2015

Energy Environ. Sci.

102

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Organic semiconductors including conjugated polymers and fullerenes continue to demonstrate promising potential for application in low-cost, printable solar cells. Power conversion efficiencies are now approaching 10 %, and major attention is increasingly turning towards identifying and overcoming the degradation mechanisms that limit the device lifetime. Recent advances in the performance of organic photovoltaics have largely arisen through the development of novel molecular structures using a donor-acceptor copolymer motif. Copolymers incorporating diketopyrrolopyrrole (DPP) units have attracted strong widespread interest, but the main role of this unit in the optoelectronic properties and device performance is not yet clear. This work investigates the natures of the main optical absorption transitions of DPP-based copolymers and chal-lenges the assumption that the DPP-unit behaves as a traditional acceptor unit. This insight leads to a clearer understanding of the excitation energy dependent photodegradation mechanism of the materials, providing ways to improve the operational stability of DPP-based solar cells. ABSTRACTDonor-acceptor copolymers are an important class of conjugated polymer on account of their chemically tunable energy levels and ambipolar charge transport properties. These materials typically exhibit two strong absorption bands in the UV-visible range, whose natures have previously been explored using theoretical analyses. In this work, we experimentally elucidate the electronic origins of these transitions and consider their effects on photostability using resonant Raman spectroscopy and transient absorption spectroscopy. In particular, we identify two dominant electronic transitions for a material comprising diketopyrrolopyrrole (DPP) acceptor and selenophene donor units: a strong transition at low energy (520-1150 nm) that is localised within the DPP unit, and a much weaker transition at higher energy (320-520 nm) that is delocalised along the conjugated backbone of both the DPP and selenophene units. The polymer is found to have good photostability under prolonged excitation in the low energy absorption band, but is much less stable to higher energy excitation. In this latter case, the selenophene ring is identified as the photodegradation site. These effects are correlated with ultrafast transient absorption spectroscopy results, which associate the photodegradation with a higher yield of polaron pairs arising from excitation of the higher energy transition. Our findings provide insight into the design of photostable low energy gap conjugated copolymers for application in organic photovoltaic devices and demonstrate a specific vulnerability of the selenophene donor unit.

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“…19,20 We have previously reported on a fluorene-based polymer (Red F, Scheme 1) containing the thiophene-benzothiadiazole-thiophene (TBT) luminophore [21][22][23][24][25] and on molecular glasses with the same luminophore 26 that readily access this wavelength range. Other examples include compounds with a 1,4-diketo-2,3,5,6-tetraphenyl-pyrrolo [3,4-c]pyrrole (DPP) core and 9,9-dialkylfluorene branches 27 and inert polymers with dispersed molecular dyes, for example PMMA/Rhodamine-640 blends. 28,29 Polythiophenes that emit at red wavelengths can be used to make lasers, for example, regiorandom poly(3-hexylthiophene) (RRa-P3HT) and blends with a small fraction of regioregular (RR-) P3HT dispersed in a RRa-P3HT matrix are effective gain media for microring lasers.…”

Section: Introductionmentioning

confidence: 99%

Efficient optical gain media comprising binary blends of poly(3-hexylthiophene) and poly(9,9-dioctylfluorene-co-benzothiadiazole)

Xia

Stavrinou

Bradley

et al. 2012

Journal of Applied Physics

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Articles you may be interested inImprovement in power conversion efficiency by blending of poly(3,4ethylenedioxythiophene):poly(styrenesulfonate) into poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester active layer Appl. Phys. Lett. 100, 223901 (2012); 10.1063/1.4723571High-efficiency blue multilayer polymer light-emitting diode based on poly(9,9-dioctylfluorene) Efficient blue-green and white light-emitting electrochemical cells based on poly[9,9-bis(3,6-dioxaheptyl)fluorene-2,7-diyl]We report the results of a study of the optical gain properties of binary blend films of regioregular poly(3-hexylthiophene) (RR-P3HT) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT). Efficient optical gain is observed in the 10-20 wt. % RR-P3HT composition range and can be tuned to the $650 nm window utilised for polymer optical fibre data-communications, with maximum gain $50 cm À1 . At higher P3HT fractions, gain thresholds increase substantially, consistent with the observed concomitant improvement in photocharge generation. Distributed feed back lasers with one-dimensional gratings exhibit pump pulse thresholds as low as 8 nJ (26 lJ cm À2 , 2.17 kW cm À2 ), lower than many other polymer-based gain media in this wavelength range. They also provide relatively high slope efficiencies >2%. The confluence of efficient optical gain with electronic properties that are conducive to charge carrier injection and transport is relatively novel and is expected to be a necessary requirement for the achievement of electrically pumped lasing. V C 2012 American Institute of Physics. [http://dx.

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Well‐Defined and Monodisperse Linear and Star‐Shaped Quaterfluorene‐DPP Molecules: the Significance of Conjugation and Dimensionality

Cited by 50 publications

References 36 publications

Novel electrochemiluminescent materials for sensor applications

Novel electrochemiluminescent materials for sensor applications

Natures of optical absorption transitions and excitation energy dependent photostability of diketopyrrolopyrrole (DPP)-based photovoltaic copolymers

Efficient optical gain media comprising binary blends of poly(3-hexylthiophene) and poly(9,9-dioctylfluorene-co-benzothiadiazole)

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