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 |
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
- Chemistry(all)