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.…
Subtitle (English): | Dedicated to Prof. Sariciftci on the occasion of his 60th birthday |
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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): | CC BY: Creative-Commons-Lizenz: Namensnennung 4.0 International |