Block Copolymer as a Nanostructuring Agent for High‐Efficiency and Annealing‐Free Bulk Heterojunction Organic Solar Cells

Renaud, Cédric; Mougnier, Sébastien Jun; Pavlopoulou, Eleni; Brochon, Cyril; Fleury, Guillaume; Deribew, Dargie; Portale, Giuseppe; Cloutet, Éric; Chambon, Sylvain; Vignau, Laurence; Hadziioannou, Georges

doi:10.1002/adma.201104461

Cited by 72 publications

(66 citation statements)

References 44 publications

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“…[8][9][10]13] The tendency of fullerenes to diffuse through the polymer phase resulting in the formation of large fullerene crystals via Ostwald ripening is regarded as the primary cause. Several techniques have been developed over the last decade to improve the thermal stability of polymer:fullerene blends including the use of high glass transition temperature polymers, [14] ternary blends with compatibilizers such as block copolymers, [15][16][17] amorphous fullerene derivatives, [18,19] donor-acceptor systems with enhanced interactions, [20,21] functionalized side chains on the polymer, [22] thermocleavable polymers, [23] light-induced fullerene polymerization, [24,25] and cross-linkable materials. [26,27] Furthermore, it was shown that mixtures of different fullerenes can improve the thermal stability of BHJs.…”

Section: Introductionmentioning

confidence: 99%

Toward High‐Temperature Stability of PTB7‐Based Bulk Heterojunction Solar Cells: Impact of Fullerene Size and Solvent Additive

Dkhil

Pfannmöller

Saba

et al. 2016

Advanced Energy Materials

105

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The use of fullerene as acceptor limits the thermal stability of organic solar cells at high temperatures as their diffusion inside the donor leads to phase separation via Ostwald ripening. Here it is reported that fullerene diffusion is fully suppressed at temperatures up to 140 °C in bulk heterojunctions based on the benzodithiophene‐based polymer (the poly[[4,8‐bis[(2‐ethylhexyl)oxy]‐benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]‐thieno[3,4‐b]thiophenediyl]], (PTB7) in combination with the fullerene derivative [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC70BM). The blend stability is found independently of the presence of diiodooctane (DIO) used to optimize nanostructuration and in contrast to PTB7 blends using the smaller fullerene derivative PC70BM. The unprecedented thermal stability of PTB7:PC70BM layers is addressed to local minima in the mixing enthalpy of the blend forming stable phases that inhibit fullerene diffusion. Importantly, although the nanoscale morphology of DIO processed blends is thermally stable, corresponding devices show strong performance losses under thermal stress. Only by the use of a high temperature annealing step removing residual DIO from the device, remarkably stable high efficiency solar cells with performance losses less than 10% after a continuous annealing at 140 °C over 3 days are obtained. These results pave the way toward high temperature stable polymer solar cells using fullerene acceptors.

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Section: Introductionmentioning

confidence: 99%

Toward High‐Temperature Stability of PTB7‐Based Bulk Heterojunction Solar Cells: Impact of Fullerene Size and Solvent Additive

Dkhil

Pfannmöller

Saba

et al. 2016

Advanced Energy Materials

105

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“…With the thermal stability of all-polymer and polymer-fullerene blend microstructures being particularly problematic [19], block copolymers present a potential solution. Indeed, it has been shown that when block copolymers are used as additives in bulk heterojunction donor–acceptor blend layers, the morphology of the resulting ternary blend film can be more stable over long periods of time, even under thermal annealing [14,20–21]. …”

Section: Introductionmentioning

confidence: 99%

Comparing blends and blocks: Synthesis of partially fluorinated diblock polythiophene copolymers to investigate the thermal stability of optical and morphological properties

Boufflet

Wood²,

Wade³

et al. 2016

Beilstein J. Org. Chem.

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SummaryThe microstructure of the active blend layer has been shown to be a critically important factor in the performance of organic solar devices. Block copolymers provide a potentially interesting avenue for controlling this active layer microstructure in solar cell blends. Here we explore the impact of backbone fluorination in block copolymers of poly(3-octyl-4-fluorothiophene)s and poly(3-octylthiophene) (F-P3OT-b-P3OT). Two block co-polymers with varying block lengths were prepared via sequential monomer addition under Kumada catalyst transfer polymerisation (KCTP) conditions. We compare the behavior of the block copolymer to that of the corresponding homopolymer blends. In both types of system, we find the fluorinated segments tend to dominate the UV–visible absorption and molecular vibrational spectral features, as well as the thermal behavior. In the block copolymer case, non-fluorinated segments appear to slightly frustrate the aggregation of the more fluorinated block. However, in situ temperature dependent Raman spectroscopy shows that the intramolecular order is more thermally stable in the block copolymer than in the corresponding blend, suggesting that such materials may be interesting for enhanced thermal stability of organic photovoltaic active layers based on similar systems.

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“…A GISAXS/GIWAXS setup has already been successfully used to study the structure of thin polymeric films (Renaud et al, 2012) and to monitor the structure formation during spin coating. However, in this manuscript we will discuss only experiments using the conventional transmission geometry.…”

Section: Beamline Descriptionmentioning

confidence: 99%

Polymer crystallization studies under processing-relevant conditions at the SAXS/WAXS DUBBLE beamline at the ESRF

et al. 2013

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Recent developments on the experimental infrastructure and the acquisition of new detectors on the Dutch-Belgian beamline BM26B at the ESRF offer novel and promising possibilities for synchrotron X-ray experiments in the field of polymer crystallization under processing-relevant conditions. In this contribution, some of the most recent experiments mimicking conditions similar to those relevant for the plastics processing industry are discussed. Simultaneous thermal analysis and wide-angle X-ray scattering (WAXS) experiments, at the millisecond time-frame level, on -nucleated isotactic polypropylene (i-PP) samples subjected to ballistic cooling up to 230 K s À1 , show that the efficiency of the nucleating agent can be suppressed when quenched cooling rates higher than 130 K s À1 are used. In situ WAXS experiments using small-scale industrial equipment during a real film blowing process reveal the dependence of the onset of crystallinity (the so-called freeze line) and the crystal orientation as a function of different take-up and blow-up ratios. In situ small-angle X-ray scattering (SAXS) experiments during high-flow fields reveal the formation of shish and kebab structures in i-PP as a function of the imposed stress. Quantitative analysis of i-PP flow-induced structures is presented. The beamline specifications required to obtain high quality and industrially relevant results are also briefly reported.

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Block Copolymer as a Nanostructuring Agent for High‐Efficiency and Annealing‐Free Bulk Heterojunction Organic Solar Cells

Cited by 72 publications

References 44 publications

Toward High‐Temperature Stability of PTB7‐Based Bulk Heterojunction Solar Cells: Impact of Fullerene Size and Solvent Additive

Toward High‐Temperature Stability of PTB7‐Based Bulk Heterojunction Solar Cells: Impact of Fullerene Size and Solvent Additive

Comparing blends and blocks: Synthesis of partially fluorinated diblock polythiophene copolymers to investigate the thermal stability of optical and morphological properties

Polymer crystallization studies under processing-relevant conditions at the SAXS/WAXS DUBBLE beamline at the ESRF

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