Abstract
Organic photovoltaics incorporating non-fullerene acceptors based on perylenediimide (PDI) now rival fullerene acceptor-based devices in performance, although the mechanisms of charge generation in PDI-based devices are not yet fully understood. Fullerene-based systems are proposed to undergo electron transfer directly from the photoexcited donor into a band of delocalized acceptor states, thus increasing charge generation efficiency. Similarly, anion delocalization has been shown to enhance the rate of electron transfer from a photoexcited donor to two electronically coupled PDI acceptors. Here we investigate how additional electron acceptors may further increase the rate of electron transfer from the donor zinc meso-tetraphenylporphyrin (ZnTPP) to an aggregate of PDI acceptors (PDI3). Femtosecond transient visible and mid-infrared absorption spectroscopies show that the rate of electron transfer from 1*ZnTPP to the PDI assembly ZnTPP2-PDI3 is statistically identical to that of the previously examined ZnTPP-PDI2. A Marcus theory analysis indicates that the parameters governing electron transfer are nearly identical for the two molecules, suggesting that the maximum electron transfer rate enhancement has been achieved in a cofacial PDI dimer because the ZnTPP directly couples to the first two PDI acceptors whereas the coupling to the third PDI is too weak.
Original language | English (US) |
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Pages (from-to) | 143-152 |
Number of pages | 10 |
Journal | Journal of Porphyrins and Phthalocyanines |
Volume | 24 |
Issue number | 1-3 |
DOIs | |
State | Published - Jan 1 2020 |
Funding
This work was supported as part of the Center for Light Energy Activated Redox Processes (LEAP), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0001059 (JMA, TJM, MRW, RMY, synthesis and spectroscopy). N.E.P-R. was supported by a NSF Graduate Research Fellowship under award number DGE-1324585. N.T.L. was supported by QNRF (Qatar National Research Fund, a member of Qatar Foundation) grant number NPRP9-174-2-092. NMR and MS measurements in this work were performed at the IMSERC at Northwestern University, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205); the State of Illinois and International Institute for Nanotechnology (IIN). We thank Dr. S. Shafaie for collecting high-resolution mass spectrometric data.
Keywords
- Marcus theory
- charge separation
- delocalization
- density of states
- electron transfer
- meso- zinc tetraphenylporphyrin
- organic photovoltaics
- perylenediimide
- transient absorption spectroscopy
- transient infrared spectroscopy
ASJC Scopus subject areas
- General Chemistry