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Unprecedented low energy losses in organic solar cells with high external quantum efficiencies by employing non-fullerene electron acceptors

Abstract

In order to realize high photocurrent generation in the low energy region of the solar spectrum, two conjugated A-D-A oligomers, PY-1 and DCI-2 comprising central dithieno[3,2-b:2′,3′-d]pyrrole donor (D) unit and end-capping acceptors (A) 1-butyl-4-methyl-2,6-dioxopyridine-3-carbonitrile (PY) or 3-dicyanomethyleneindan-1-one (DCI) have been synthesized and characterized. The oligomers showed strong absorptions in the red and near-IR region in solution and in the solid state. As a consequence of strong electron accepting character, the absorption band of DCI-2 in thin films is significantly red-shifted compared to PY-1 resulting in a low optical gap of 1.23 eV. In optimized solution-processed bulk-heterojunction solar cells using a polymeric donor P1, the new non-fullerene acceptor DCI-2 provide an excellent power conversion efficiency of 6.94% which is noticeably higher than for PY-1-based devices (PCE = 4.89%). Most importantly, a high open-circuit voltage (Voc) of ~0.8 V with unprecedented energy losses, between optical energy gap and open-circuit voltage, between 0.39-0.43 eV concomitant with excellent external quantum efficiencies of 69%@880 nm in the NIR-regime have been achieved for DCI-2 based devices.

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Publication details

The article was accepted on 13 Jun 2017 and first published on 13 Jun 2017


Article type: Paper
DOI: 10.1039/C7TA04703G
Citation: J. Mater. Chem. A, 2017, Accepted Manuscript
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    Unprecedented low energy losses in organic solar cells with high external quantum efficiencies by employing non-fullerene electron acceptors

    A. Mishra, M. L. Keshtov, A. Looser, R. Singhal, M. Stolte, F. Würthner, P. Baeuerle and G. D. Sharma, J. Mater. Chem. A, 2017, Accepted Manuscript , DOI: 10.1039/C7TA04703G

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