DataVXACS Energy LettersPaper
journal article·2019-09-13Open access

Impact of Marginal Exciton–Charge-Transfer State Offset on Charge Generation and Recombination in Polymer:Fullerene Solar Cells

Michelle S. Vezie, Mohammed Azzouzi, Andrew M. Telford, Thomas R. Hopper, Alexander B. Sieval, Jan C. Hummelen, Kealan Fallon, Hugo Bronstein, Thomas Kirchartz, Artem A. Bakulin, Tracey M. Clarke, Jenny Nelson

ACS Energy Letters· Volume 4· Issue 9
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Source abstract

Abstract

The energetic offset between the initial photoexcited state and charge-transfer (CT) state in organic heterojunction solar cells influences both charge generation and open-circuit voltage (Voc). Here, we use time-resolved spectroscopy and voltage loss measurements to analyze the effect of the exciton–CT state offset on charge transfer, separation, and recombination processes in blends of a low-band-gap polymer (INDT-S) with fullerene derivatives of different electron affinity (PCBM and KL). For the lower exciton–CT state offset blend (INDT-S:PCBM), both photocurrent generation and nonradiative voltage losses are lower. The INDT-S:PCBM blend shows different excited-state dynamics depending on whether the donor or acceptor is photoexcited. Surprisingly, the charge recombination dynamics in INDT-S:PCBM are distinctly faster than those in INDT-S:KL upon excitation of the donor. We reconcile these observations using a kinetic model and by considering hybridization between the lowest excitonic and CT states. The modeling results show that this hybridization can significantly reduce Voc losses while still allowing reasonable charge generation efficiency.
Source: openalex_inverted_index · Quality: baseline

Research context

Polymers

OpenAlex topics: Organic Electronics and Photovoltaics · Conducting polymers and applications · Perovskite Materials and Applications

SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.

Affiliations

Department of Physics and Centre for Plastic Electronics, Imperial College London, London SW7 2AZ, United Kingdom

Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London SW7 2AZ, United Kingdom

Solenne BV, Zernikepark 6, 9747AN Groningen, The Netherlands

Stratingh Institute for Chemistry & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AN Groningen, The Netherlands

Department of Chemistry, University College London, Christopher Ingold Building, London WC1H 0AJ, United Kingdom

Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom

IEK5-Photovoltaics, Forschungszentrum Jülich, 52425 Jülich, Germany

Faculty of Engineering and CENIDE, University of Duisburg−Essen, Carl-Benz-Strasse 199, 47057 Duisburg, Germany

Funding

Engineering and Physical Sciences Research Council · Horizon 2020 Framework Programme · H2020 European Research Council

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