Picosecond Capture of Photoexcited Electrons Improves Photovoltaic Conversion in MAPbI<sub>3</sub> :C<sub>70</sub> -Doped Planar and Mesoporous Solar Cells.
basic_science · Level V
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- Record sourced from PubMed, PMID 30141198.
- Also identified by DOI 10.1002/adma.201801496.
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Abstract
In this work, solar cells based on methylammonium lead iodide (MAPbI<sub>3</sub> ) doped in solution with C<sub>70</sub> fullerene in a mesoporous as well as planar electron-transporting layer (ETL)-free architecture are realized, showcasing in the latter case a record efficiency of 15.7% and an improved open-circuit voltage (V<sub>OC</sub> ). Contrary to the bulk heterojunction previously reported, the C<sub>70</sub> molecules do not phase segregate and they are rather finely dispersed in the perovskite film, possibly infiltrating at the grain boundaries, while assisting the growth of a highly uniform perovskite layer. By means of time-resolved femtosecond-to-nanosecond optical spectroscopy, with an extended spectral coverage, it is observed that electrons photogenerated in the perovskite are transferred to C<sub>70</sub> with a time constant of 20 ps. Despite being captured by C<sub>70</sub> , electrons are not deeply trapped and can potentially bounce back into the perovskite, as suggested by the high fill factor and enhanced V<sub>OC</sub> of the MAPbI<sub>3</sub> :C<sub>70</sub> solar cells, especially in the case of the ETL-free device configuration.