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Time evolution studies of dithieno[3,2-b:2′,3′-d]pyrrole-based A–D–A oligothiophene bulk heterojunctions during solvent vapor annealing towards optimization of photocurrent generation

Ludovic Escoubas 1 Dario Cozza 1 Carmen Ruiz 1 David Duché 2 Jean Jacques Simon 1 Ben Sadok Martin Pfannmöllerpfannm¨pfannmöller Ibrahim Ata David Duchéduch´duché Meriem Gaceur 3 Tomoyuki Koganezawa Noriyuki Yoshimoto Jean-Jacques Simon 2 Christine Videlot-Ackermann 3 Olivier Margeat 3 Sara Bals 4 B Peter Jörg Ackermann Sadok Ben Dkhil 3 Martin Pfannmöller Peter Bäuerle
1 IM2NP - Institut des Matériaux, de Microélectronique et des Nanosciences de Provence
2 OPTO-PV
IM2NP - Institut des Matériaux, de Microélectronique et des Nanosciences de Provence
3 CINaM - Centre Interdisciplinaire de Nanoscience de Marseille
4 Univ Antwerp, Electron Microscopy Mat Sci EMAT, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
Abstract : Solvent vapor annealing (SVA) is one of the main techniques to improve the morphology of bulk heterojunction solar cells using oligomeric donors. In this report, we study time evolution of nanoscale morphological changes in bulk heterojunctions based on a well-studied dithienopyrrole-based A–D–A oligothiophene (dithieno[3,2-b:2 0 ,3 0-d]pyrrole named here 1) blended with [6,6]-phenyl-C 71-butyric acid methyl ester (PC 71 BM) to increase photocurrent density by combining scanning transmission electron microscopy and low-energy-loss spectroscopy. Our results show that SVA transforms the morphology of 1 : PC 71 BM blends by a three-stage mechanism: highly intermixed phases evolve into nanostructured bilayers that correspond to an optimal blend morphology. Additional SVA leads to completely phase-separated micrometer-sized domains. Optical spacers were used to increase light absorption inside optimized 1 : PC 71 BM blends leading to solar cells of 7.74% efficiency but a moderate photocurrent density of 12.3 mA cm À2. Quantum efficiency analyses reveal that photocurrent density is mainly limited by losses inside the donor phase. Indeed, optimized 1 : PC 71 BM blends consist of large donor-enriched domains not optimal for exciton to photocurrent conversion. Shorter SVA times lead to smaller domains; however they are embedded in large mixed phases suggesting that introduction of stronger molecular packing may help us to better balance phase separation and domain size enabling more efficient bulk heterojunction solar cells.
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https://hal-amu.archives-ouvertes.fr/hal-01788908
Contributor : Ludovic Escoubas <>
Submitted on : Wednesday, May 9, 2018 - 3:18:28 PM
Last modification on : Friday, January 24, 2020 - 11:22:06 AM

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UNIV-AMU | CNRS | UNIV-TLN | IM2NP | CINAM

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Ludovic Escoubas, Dario Cozza, Carmen Ruiz, David Duché, Jean Jacques Simon, et al.. Time evolution studies of dithieno[3,2-b:2′,3′-d]pyrrole-based A–D–A oligothiophene bulk heterojunctions during solvent vapor annealing towards optimization of photocurrent generation. Journal of Materials Chemistry A, Royal Society of Chemistry, 2017, 5 (3), pp.1005 - 1013. ⟨10.1039/c6ta08175d⟩. ⟨hal-01788908⟩

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