1. Impact of Fullerene Mixing Behavior on the Microstructure, Photophysics, and Device Performance of Polymer/Fullerene Solar Cells
- Author
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Shyamal K. K. Prasad, Dinesh Kabra, Naresh Chandrasekaran, Justin M. Hodgkiss, Eliot Gann, Wenchao Huang, Christopher R. McNeill, Lars Thomsen, and Yi-Bing Cheng
- Subjects
Morphology ,Photoluminescence ,Fullerene ,Materials science ,Organic solar cell ,Mobility Conjugated Polymer ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,7. Clean energy ,01 natural sciences ,Polymer solar cell ,Ultrafast laser spectroscopy ,Physics::Atomic and Molecular Clusters ,Organic Photovoltaic Cells ,General Materials Science ,High-Efficiency ,Spectroscopy ,Charge Separation ,chemistry.chemical_classification ,Molecular-Orientation ,Organic Solar Cells ,Miscibility ,Polymer ,Semiconductor ,021001 nanoscience & nanotechnology ,Acceptor ,0104 chemical sciences ,Photophysics ,chemistry ,Chemical engineering ,Blends ,13. Climate action ,Mixing Behavior ,Device Physics ,Fullerenes ,0210 nano-technology ,Domain Purity - Abstract
Here, a comprehensive study of the influence of polymer:fullerene mixing behavior on the performance, thin-film microstructure, photophysics, and device physics of polymer solar cells is presented. In particular, blends of the donor polymer PBDTTT-EFT with the acceptor PC71BM that exhibit power conversion efficiencies over 9% are investigated. Through tuning of the fullerene concentration in PBDTTT-EFT:PC71BM blends, the impact of fullerene mixing behavior is systematically investigated via a combination of synchrotron-based X-ray scattering and spectroscopy techniques. The impact of fullerene loading on photophysics and device physics is further explored with steady-state photoluminescence measurements, ultrafast transient absorption spectroscopy, and transient photovoltage measurements. In the low fullerene concentration regime (70 wt %), large fullerene domains result in incomplete PC71BM exciton harvesting with the presence of fullerene molecules also disrupting the molecular packing of polymer crystallites. The optimum fullerene concentration of similar to 60-67 wt % balances the requirements of charge generation and charge collection. These findings demonstrate that controlling the fullerene concentration in the mixed phase and optimizing the balance between pure and mixed phases are critical for maximizing the efficiency of highly mixed polymer/fullerene solar cells.
- Published
- 2016