Incomplete Exciton Harvesting from Fullerenes in Bulk Heterojunction Solar Cells

Department of Applied Physics, Stanford University, Stanford, California 94305, USA.
Nano Letters (Impact Factor: 13.59). 10/2009; 9(12):4037-41. DOI: 10.1021/nl902205n
Source: PubMed


We investigate the internal quantum efficiencies (IQEs) of high efficiency poly-3-hexylthiophene:[6,6]-phenyl-C(61)-butyric acid methyl ester (P3HT:PCBM) solar cells and find them to be lower at wavelengths where the PCBM absorbs. Because the exciton diffusion length in PCBM is too small, excitons generated in PCBM decay before reaching the donor-acceptor interface. This result has implications for most state of the art organic solar cells, since all of the most efficient devices use fullerenes as electron acceptors.

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    • "Work has also been carried out to compare the absorption of P3HT and PCBM and concluded that the low absorption of PCBM needs to be offset by P3HT to form an efficient device. This study was also able to make an estimate of the exciton collection from various phases of P3HT: PCBM devices, as we propose to do in this article [9]. Interesting predictions of the device morphology combined with Monte Carlo simulations can also provide accurate estimates of the charge collection, but this data lacks detailed information about the bulk morphology [10]. "
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