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Charge transfer in ternary solar cells employing two fullerene derivatives: where do electrons go?

Please always quote using this URN: urn:nbn:de:bvb:20-opus-257506
  • Earlier reports demonstrated that ternary organic solar cells (OSC) made of donor polymers (D) blended with different mixtures of fullerene acceptors (A : A) performed very similarly. This finding is surprising, as the corresponding fullerene LUMO levels are slightly different, which might result in decisive differences in the charge transfer step. We investigate ternary OSC (D : A : A) made of the donor polymer P3HT with stoichiometric mixtures of different fullerene derivatives, PC\(_{60}\)BM : PC\(_{70}\)BM and PC\(_{70}\)BM : IC\(_{60}\)BA,Earlier reports demonstrated that ternary organic solar cells (OSC) made of donor polymers (D) blended with different mixtures of fullerene acceptors (A : A) performed very similarly. This finding is surprising, as the corresponding fullerene LUMO levels are slightly different, which might result in decisive differences in the charge transfer step. We investigate ternary OSC (D : A : A) made of the donor polymer P3HT with stoichiometric mixtures of different fullerene derivatives, PC\(_{60}\)BM : PC\(_{70}\)BM and PC\(_{70}\)BM : IC\(_{60}\)BA, respectively. Using quantitative electron paramagnetic resonance (EPR) we can distinguish between positive and negative polarons, localized on the specific molecules. We found that after the initial charge transfer step, the electrons are re-distributed over two nearby acceptors in agreement with their stoichiometry and their relative LUMO energy difference. Remarkably, the measured ΔLUMO differences in fullerene mixtures are reduced by an order of magnitude compared to that of the pristine materials, i. e., below 1 meV for PC\(_{60}\)BM : PC\(_{70}\)BM and (20±5) meV for PC\(_{70}\)BM : IC\(_{60}\)BA. Furthermore, we found that this reduced ΔLUMO explains the shift in open circuit voltage for D : A : A organic solar cells. We attribute these findings to hybridization, leading to an effective fullerene LUMO. Consequently, multi-acceptor blends are indeed a viable option for photodetectors and solar cells, as they combine the best electron acceptor and light absorbing properties.show moreshow less

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Metadaten
Subtitle (English):Dedicated to Prof. Sariciftci on the occasion of his 60th birthday
Author: Andreas Sperlich, Michael Auth, Vladimir DyakonovORCiD
URN:urn:nbn:de:bvb:20-opus-257506
Document Type:Journal article
Faculties:Fakultät für Physik und Astronomie / Physikalisches Institut
Language:English
Parent Title (English):Israel Journal of Chemistry
Year of Completion:2022
Volume:62
Issue:7-8
Article Number:e202100064
Source:Israel Journal of Chemistry (2022) 62:7-8, e202100064. https://doi.org/10.1002/ijch.202100064
DOI:https://doi.org/10.1002/ijch.202100064
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
Tag:ternary organic solar cells
Release Date:2022/09/20
Licence (German):License LogoCC BY: Creative-Commons-Lizenz: Namensnennung 4.0 International