Regensburg 2019 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 50: Organic Electronics and Photovoltaics III - Organic Photovoltaics
CPP 50.9: Vortrag
Donnerstag, 4. April 2019, 11:45–12:00, H18
Absence of charge transfer state enables very low VOC losses in SWCNT:fullerene solar cells — •Andrej Classen1, Lukas Einsiedler1, Thomas Heumüller1, Arko Graf2, Maximilian Brohmann2, Felix Berger2, Simon Kahmann1, Moses Richter1, Gebhard Matt1, Karen Forberich1, Jana Zaumseil2, and Christoph Brabec1 — 1Friedrich-Alexander-Universität Erlangen-Nürnberg — 2Ruprecht-Karls-Universität Heidelberg
Current state of the art organic solar cells (OSC) still suffer from high losses of open circuit voltage (VOC). Conventional polymer:fullerene solar cells usually exhibit band gap to VOC losses greater than 0.8 V. Here a detailed investigation of VOC is presented for solution processed OSCs based on (6,5) single-walled carbon nanotubes (SWCNT):[6,6]-phenyl-C71-butyric acid methyl ester (PC70BM) active layers [1]. Considering the very small optical band gap of only 1.22 eV of (6,5) SWCNTs, a high VOC of 0.59 V leading to a low Egap/q - VOC = 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, VOC losses attributed to a broadening of the band edge are very small resulting in VOC,SQ - VOC,rad = 0.12 V. Interestingly, this loss is mainly caused by minor amounts of SWCNTs with smaller band gaps as well as (6,5) SWCNT trions. More intriguingly, we find a very low voltage loss due to nonradiative recombination, ΔVOC,nonrad = 0.26 V, which is exceptional for fullerene based OSCs.
[1] Classen et al., Adv. Energy Mater., 2018, 1801913