Discerning Performance Bottlenecks of State‐of‐the‐Art Narrow Bandgap Organic Solar Cells
Source abstract
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 (Eg≈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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Research context
OpenAlex topics: Organic Electronics and Photovoltaics · Semiconductor materials and interfaces · Thin-Film Transistor Technologies
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
Affiliations
Institute of Physics and Astronomy University of Potsdam Karl‐Liebknecht‐Str. 24–25 14476 Potsdam‐Golm Germany
Max Planck Institute for Polymer Research Ackermannweg 10 55128 Mainz Germany
Paul‐Drude‐Institut für Festkörperelektronik Leibniz‐Institut im Forschungsverbund Berlin e.V. Hausvogteiplatz 5–7 10117 Berlin Germany
Institute of Chemistry Chinese Academy of Sciences 2 North 1st Street Haidian Beijing 100190 China
Sustainable Advanced Materials (Sêr SAM) Centre for Integrative Semiconductor Materials (CISM) Department of Physics Swansea University Singleton Park Swansea SA1 8EN UK
Australian Institute for Bioengineering and Nanotechnology The University of Queensland Brisbane Queensland 4072 Australia
School of Mathematics and Physics The University of Queensland St Lucia Brisbane QLD 4072 Australia
NCD‐SWEET Beamline ALBA Synchrotron Light Source Cerdanyola del Vallès Barcelona 08290 Spain
Semiconductor Physics and Research Center for Materials Architectures and Integration of Nanomembranes (MAIN) TU Chemnitz 09107 Chemnitz Germany
Funding
Australian Research Council · Engineering and Physical Sciences Research Council · European Regional Development Fund · Volkswagen Foundation · King Abdullah University of Science and Technology · Deutsche Forschungsgemeinschaft
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