Abstract
Semiconducting single-walled carbon nanotubes (s-SWCNTs) are promising for solution-processed, thin film photovoltaics due to their strong near-infrared absorptivity and excellent transport properties. We report on the generation yield and recombination kinetics of free charge carriers in photoexcited thin films of polymer-wrapped s-SWCNTs with and without an overlying electron-accepting C60 layer, using time-resolved microwave photoconductivity (TRMC). Free carriers are generated in neat s-SWCNT films, even without an obvious driving force for exciton dissociation. However, most carriers recombine in <10 ns. Adding C60 increases the yield and extends the lifetime of a significant fraction of free carriers to ≫100 ns via interfacial charge separation. Spectral dependencies indicate that the driving force for interfacial electron transfer vanishes for large-diameter SWCNTs, from which we approximate (9,7) s-SWCNT energetics. We estimate a free carrier generation yield of ∼6% in neat s-SWCNT films and 9 GHz SWCNT hole mobility of >1.3 cm2 V-1 s-1. These studies improve understanding of s-SWCNT photoresponses in solar cells and photodetectors.
Original language | American English |
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Pages (from-to) | 3550-3559 |
Number of pages | 10 |
Journal | Journal of Physical Chemistry Letters |
Volume | 4 |
Issue number | 21 |
DOIs | |
State | Published - 7 Nov 2013 |
NREL Publication Number
- NREL/JA-5900-60218
Keywords
- C
- exciton
- fullerene
- lifetime
- near-infrared
- photovoltaic
- time-resolved microwave conductivity