20 April 2006 Modeling of poly(3-hexylthiophene): methanofullerene bulk-heterojunction solar cells
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Abstract
Bulk-heterojunction solar cells made from blend films of regioregular poly(3-hexylthiophene) (P3TH) and methanofullerene (PCBM) exhibit a ten-fold increase of the power conversion efficiency upon post production annealing. We have applied a numerical model to explain this dramatic enhancement of the efficiency. The mobilities of electrons and holes were selectively determined, and it was found that the hole mobility of P3HT in the blend increases by more than three orders of magnitude. Moreover, upon annealing the absorption spectrum of P3HT:PCBM blends undergo a strong red-shift, improving the spectral overlap with the solar emission, which result in an increase of more than 60% in the generation rate of charge carriers. Our numerical model demonstrates that the unannealed devices suffer from the buildup of space-charge, as a consequence of the low hole mobility. Furthermore, at short-circuit the dissociation efficiency of bound electron-hole pairs at the donor/acceptor interface is close to 90%, which explains the large quantum efficiencies measured in P3HT:PCBM blends.
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L. Jan Anton Koster, L. Jan Anton Koster, Valentin D. Mihailetchi, Valentin D. Mihailetchi, Bert de Boer, Bert de Boer, Paul W. M. Blom, Paul W. M. Blom, "Modeling of poly(3-hexylthiophene): methanofullerene bulk-heterojunction solar cells", Proc. SPIE 6192, Organic Optoelectronics and Photonics II, 61920A (20 April 2006); doi: 10.1117/12.664508; https://doi.org/10.1117/12.664508
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