Spin signatures of photogenerated radical anions in polymer-[70]fullerene bulk-heterojunctions : high-frequency pulsed EPR spectroscopy.
- Chemical Sciences and Engineering Division
Charged polarons in thin films of polymer-fullerene composites are investigated by light-induced electron paramagnetic resonance (EPR) at 9.5 GHz (X-band) and 130 GHz (D-band). The materials studied were poly(3-hexylthiophene) (PHT), [6,6]-phenyl-C61-butyric acid methyl ester (C{sub 60}-PCBM), and two different soluble C{sub 70}-derivates: C{sub 70}-PCBM and diphenylmethano[70]fullerene oligoether (C{sub 70}-DPM-OE). The first experimental identification of the negative polaron localized on the C{sub 70}-cage in polymer-fullerene bulk heterojunctions has been obtained. When recorded at conventional X-band EPR, this signal is overlapping with the signal of the positive polaron, which does not allow for its direct experimental identification. Owing to the superior spectral resolution of the high frequency D-band EPR, we were able to separate light-induced signals from P{sup +} and P{sup -} in PHT-C{sub 70} bulk heterojunctions. Comparing signals from C{sub 70}-derivatives with different side-chains, we have obtained experimental proof that the polaron is localized on the cage of the C{sub 70} molecule.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); MICNN of Spain; CAM
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 1021329
- Report Number(s):
- ANL/CSE/JA-70708; TRN: US201116%%722
- Journal Information:
- J. Phys. Chem. B, Vol. 114, Issue 45 ; Apr. 14, 2010
- Country of Publication:
- United States
- Language:
- ENGLISH
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