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Effect of active layer morphology on recombination mechanism in polymer: fullerene organic bulk heterojunction solar cells

Published online by Cambridge University Press:  18 April 2012

Pavel Dutta
Affiliation:
Department of Electrical Engineering, South Dakota State University, Brookings, SD 57007, USA
Mukesh Kumar
Affiliation:
Department of Electrical Engineering, South Dakota State University, Brookings, SD 57007, USA
Monika Rathi
Affiliation:
Nanoscience and Nanoengineering Department, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
Phil Ahrenkiel
Affiliation:
Nanoscience and Nanoengineering Department, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA
David Galipeau
Affiliation:
Department of Electrical Engineering, South Dakota State University, Brookings, SD 57007, USA
Venkat Bommisetty
Affiliation:
Department of Electrical Engineering, South Dakota State University, Brookings, SD 57007, USA
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Abstract

The effect of phase separation of the donor-acceptor (DA) blend on the dominant recombination mechanism in polymer-fullerene [(poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM)] based bulk heterojunction (BHJ) cells has been investigated. Coarse (70-150 nm) and fine (20-25 nm) phase separated blends and corresponding devices were prepared using chlorobenzene (CB) and ortho-dichlorobenzene (1,2-DCB) as spin casting solvents respectively. Nanoscale mobility measurements indicated highly unbalanced charge transport in coarse morphology based (CB cast) devices. Linear dependence of short circuit current (Jsc) vs. light intensity (I) suggested first order monomolecular (MR) recombination in the fine phase separated devices (1,2-DCB cast) whereas sub-linearity suggested dominant role of bimolecular (BR) recombination in coarse phase separated devices (CB cast). Improved device efficiency of 1,2-DCB based devices (η ≈ 2.54 %) compared to CB (η ≈ 0.9 %) may be attributed to reduced BR recombination as a result of finer phase separation.

Type
Research Article
Copyright
Copyright © Materials Research Society 2012

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References

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