Discerning Performance Bottlenecks of State‐of‐the‐Art Narrow Bandgap Organic Solar Cells

Abstract Discerning loss mechanisms in organic solar cells with narrow optical bandgap is critical for the development of conventional and next‐generation photovoltaic technologies, especially for tandem and semi‐transparent solar cells. Here, all photocurrent losses are quantitatively deconvoluted in two low‐bandgap ( E g ≈1.23 eV) binary systems using structurally analogous non‐fullerene acceptors (NFAs), namely BTPV‐4F‐eC9 and BTPV‐4Cl‐eC9. Bias‐dependent free charge generation and photoluminescence studies pinpoint geminate charge transfer (CT) state recombination as the predominant photocurrent limitation in both systems, compared to parent Y6‐blends. Transient absorption spectroscopy too reveals a critical competition between CT decay and separation dynamics. Theoretical calculations uncover multiple stable molecular conformers that restrict NFA aggregation, aligning with morphological studies, resulting in poor CT separation in photoactive blends. Owing to CT loss pathways, free charge recombination in both low‐bandgap systems is closer to the Langevin limit than in PM6:Y6. Nonetheless, they exhibit overall voltage losses of ≈0.56 V comparable to PM6:Y6, and efficient exciton dissociation despite a lower driving force. Current–voltage simulations show that suppressing geminate losses can vitally balance recombination pathways to unlock photocurrent potential of low‐bandgap blends. Further optimization of the charge carrier mobility would push the PCE >16%, moving the internal quantum efficiency toward the detailed balance limit.

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Publication Details

Journal
Advanced Energy Materials
Published
2025-05-30
DOI
https://doi.org/10.1002/aenm.202502398
Citations
4
Primary Topic
Organic Electronics and Photovoltaics
Type
article
Field-Weighted Citation Impact
2.92

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article

Discerning Performance Bottlenecks of State‐of‐the‐Art Narrow Bandgap Organic Solar Cells

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Advanced Energy Materials
Organic Electronics and Photovoltaics
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article

Discerning Performance Bottlenecks of State‐of‐the‐Art Narrow Bandgap Organic Solar Cells

Dieter Neher, Drew B. Riley, Alexander Ehm, Guorui He, Safa Shoaee, Julian A. Steele, Dietrich R. T. Zahn, Ardalan Armin, Manasi Pranav, Eduardo Solano, Mohammad Saeed Shadabroo, Yonglin Cao, Felix Lang, Lei Meng, Atul Shukla, Denis Andrienko, Yongfang Li, Yufei Gong, Davide Mascione
article en
4 citations

Abstract

Abstract Discerning loss mechanisms in organic solar cells with narrow optical bandgap is critical for the development of conventional and next‐generation photovoltaic technologies, especially for tandem and semi‐transparent solar cells. Here, all photocurrent losses are quantitatively deconvoluted in two low‐bandgap ( E g ≈1.23 eV) binary systems using structurally analogous non‐fullerene acceptors (NFAs), namely BTPV‐4F‐eC9 and BTPV‐4Cl‐eC9. Bias‐dependent free charge generation and photoluminescence studies pinpoint geminate charge transfer (CT) state recombination as the predominant photocurrent limitation in both systems, compared to parent Y6‐blends. Transient absorption spectroscopy too reveals a critical competition between CT decay and separation dynamics. Theoretical calculations uncover multiple stable molecular conformers that restrict NFA aggregation, aligning with morphological studies, resulting in poor CT separation in photoactive blends. Owing to CT loss pathways, free charge recombination in both low‐bandgap systems is closer to the Langevin limit than in PM6:Y6. Nonetheless, they exhibit overall voltage losses of ≈0.56 V comparable to PM6:Y6, and efficient exciton dissociation despite a lower driving force. Current–voltage simulations show that suppressing geminate losses can vitally balance recombination pathways to unlock photocurrent potential of low‐bandgap blends. Further optimization of the charge carrier mobility would push the PCE >16%, moving the internal quantum efficiency toward the detailed balance limit.

Advanced Energy MaterialsVol. 15(32)
The University of Queensland (AU), University of Potsdam (DE), Chinese Academy of Sciences (CN), Chemnitz University of Technology (DE), ALBA Synchrotron (Spain) (ES), Swansea University (GB), Max Planck Institute for Polymer Research (DE), Paul Drude Institute for Solid State Electronics (DE), Institute of Chemistry (CN), Forschungsverbund Berlin (DE), Institute of Physics (CN)
Deutsche Forschungsgemeinschaft, Volkswagen Foundation, King Abdullah University of Science and Technology, Engineering and Physical Sciences Research Council, Australian Research Council, European Regional Development Fund
Openalex Percentile: Top 9%
Organic Electronics and Photovoltaics
2.92
DOIOpen Access PDFOpenAlex
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