Abstract
The primary photoexcited species in excitonic semiconductors is a bound electron-hole pair, or exciton. An important strategy for producing separated electrons and holes in photoexcited excitonic semiconductors is the use of donor/acceptor heterojunctions, but the degree to which the carriers can escape their mutual Coulomb attraction is still debated for many systems. Here, we employ a combined pump-probe ultrafast transient absorption (TA) spectroscopy and time-resolved microwave conductivity (TRMC) study on a suite of model excitonic heterojunctions consisting of mono-chiral semiconducting single-walled carbon nanotube (s-SWCNT) electron donors and small-molecule electron acceptors. Comparison of the charge-separated state dynamics between TA and TRMC photoconductance reveals a quantitative match over the 0.5 microsecond time scale. Charge separation yields derived from TA allow extraction of s-SWCNT hole mobilities of ca. 1.5 cm2 V-1 s-1 (at 9 GHz) by TRMC. The correlation between the techniques conclusively demonstrates that photoinduced charge carriers separated across these heterojunctions do not form bound charge transfer states, but instead form free/mobile charge carriers.
Original language | American English |
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Pages (from-to) | 1509-1517 |
Number of pages | 9 |
Journal | Materials Horizons |
Volume | 8 |
Issue number | 5 |
DOIs | |
State | Published - May 2021 |
Bibliographical note
Publisher Copyright:© The Royal Society of Chemistry.
NREL Publication Number
- NREL/JA-5K00-78538
Keywords
- carbon nanotubes
- organic photovoltaics
- photoinduced charge transfer
- solar-photochemistry
- time-resolved spectroscopy