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Analysis of Triplet Exciton Loss Pathways in PTB7:PC\(_{71}\)BM Bulk Heterojunction Solar Cells

Please always quote using this URN: urn:nbn:de:bvb:20-opus-147413
  • A strategy for increasing the conversion efficiency of organic photovoltaics has been to increase the VOC by tuning the energy levels of donor and acceptor components. However, this opens up a new loss pathway from an interfacial charge transfer state to a triplet exciton (TE) state called electron back transfer (EBT), which is detrimental to device performance. To test this hypothesis, we study triplet formation in the high performing PTB7:PC\(_{71}\)BM blend system and determine the impact of the morphology-optimizing additive 1,8-diiodoctaneA strategy for increasing the conversion efficiency of organic photovoltaics has been to increase the VOC by tuning the energy levels of donor and acceptor components. However, this opens up a new loss pathway from an interfacial charge transfer state to a triplet exciton (TE) state called electron back transfer (EBT), which is detrimental to device performance. To test this hypothesis, we study triplet formation in the high performing PTB7:PC\(_{71}\)BM blend system and determine the impact of the morphology-optimizing additive 1,8-diiodoctane (DIO). Using photoluminescence and spin-sensitive optically detected magnetic resonance (ODMR) measurements at low temperature, we find that TEs form on PC\(_{71}\)BM via intersystem crossing from singlet excitons and on PTB7 via EBT mechanism. For DIO blends with smaller fullerene domains, an increased density of PTB7 TEs is observed. The EBT process is found to be significant only at very low temperature. At 300 K, no triplets are detected via ODMR, and electrically detected magnetic resonance on optimized solar cells indicates that TEs are only present on the fullerenes. We conclude that in PTB7:PC\(_{71}\)BM devices, TE formation via EBT is impacted by fullerene domain size at low temperature, but at room temperature, EBT does not represent a dominant loss pathway.show moreshow less

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Metadaten
Author: Hannes Kraus, Michael C. Heiber, Stefan Väth, Julia Kern, Carsten Deibel, Andreas Sperlich, Vladimir Dyakonov
URN:urn:nbn:de:bvb:20-opus-147413
Document Type:Journal article
Faculties:Fakultät für Physik und Astronomie / Physikalisches Institut
Language:English
Parent Title (English):Scientific Reports
Year of Completion:2016
Volume:6
Issue:29158
Source:Scientific Reports 6, 29158; doi: 10.1038/srep29158 (2016).
DOI:https://doi.org/10.1038/srep29158
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
Tag:electronic properties and materials; solar cells
Release Date:2017/05/11
Collections:Open-Access-Publikationsfonds / Förderzeitraum 2016
Licence (German):License LogoCC BY: Creative-Commons-Lizenz: Namensnennung