Absence of Charge Transfer State Enables Very Low V-OC Losses in SWCNT:Fullerene Solar Cells

Classen A, Einsiedler L, Heumuelier T, Graf A, Brohmann M, Berger F, Kahmann S, Richter M, Matt G, Forberich K, Zaumseil J, Brabec C (2019)

Publication Language: English

Publication Status: Published

Publication Type: Journal article

Publication year: 2019

Journal

Advanced Energy Materials Wiley

Publisher: WILEY-V C H VERLAG GMBH

Book Volume: 9

Article Number: ARTN 1801913

Journal Issue: 1

DOI: 10.1002/aenm.201801913

Abstract

Current state-of-the-art organic solar cells (OSCs) still suffer from high losses of open-circuit voltage (V-OC). Conventional polymer:fullerene solar cells usually exhibit bandgap to V-OC losses greater than 0.8 V. Here a detailed investigation of V-OC is presented for solution-processed OSCs based on (6,5) single-walled carbon nanotube (SWCNT): [6,6]-phenyl-C-71-butyric acid methyl ester active layers. Considering the very small optical bandgap of only 1.22 eV of (6,5) SWCNTs, a high V-OC of 0.59 V leading to a low E-gap/q - V-OC = 0.63 V loss is observed. The low voltage losses are partly due to the lack of a measurable charge transfer state and partly due to the narrow absorption edge of SWCNTs. Consequently, V-OC losses attributed to a broadening of the band edge are very small, resulting in V-OC,V-SQ - V-OC,V-rad = 0.12 V. Interestingly, this loss is mainly caused by minor amounts of SWCNTs with smaller bandgaps as well as (6,5) SWCNT trions, all of which are experimentally well resolved employing Fourier transform photocurrent spectroscopy. In addition, the low losses due to band edge broadening, a very low voltage loss are also found due to nonradiative recombination, Delta V-OC,V-nonrad = 0.26 V, which is exceptional for fullerene-based OSCs.

Authors with CRIS profile

Andrej Classen Institute Materials for Electronics and Energy Technology (i-MEET) Lukas Einsiedler Institute Materials for Electronics and Energy Technology (i-MEET) Simon Kahmann Institute Materials for Electronics and Energy Technology (i-MEET) Moses Richter Institute Materials for Electronics and Energy Technology (i-MEET) Gebhard Matt Institute Materials for Electronics and Energy Technology (i-MEET) Karen Forberich Institute Materials for Electronics and Energy Technology (i-MEET) Christoph Brabec Institute Materials for Electronics and Energy Technology (i-MEET)

Involved external institutions

Ruprecht-Karls-Universität Heidelberg DE Germany (DE)

How to cite

APA:

Classen, A., Einsiedler, L., Heumuelier, T., Graf, A., Brohmann, M., Berger, F.,... Brabec, C. (2019). Absence of Charge Transfer State Enables Very Low V-OC Losses in SWCNT:Fullerene Solar Cells. Advanced Energy Materials, 9(1). https://dx.doi.org/10.1002/aenm.201801913

MLA:

Classen, Andrej, et al. "Absence of Charge Transfer State Enables Very Low V-OC Losses in SWCNT:Fullerene Solar Cells." Advanced Energy Materials 9.1 (2019).

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