Role of balanced charge carrier transport in low band gap polymer: Fullerene bulk heterojunction solar cells
article
Lowering of the optical band gap of conjugated polymers in bulk heterojunction solar cells not only leads to an increased absorption but also to an increase of the optimal active layer thickness due to interference effects at longer wavelengths. The increased carrier densities due to the enhanced absorption and thicker active layers make low band gap solar cells more sensitive to formation of space charges and recombination. By systematically red shifting the optical parameters of poly[2-methoxy-5-(3′,7′- dimethyloctyloxy)-p-phenylenevinylene] and 6,6-phenyl C61-butyric acid methyl ester, we simulate the effect of a reduced band gap on the solar cell efficiencies. We show that especially the fill factor of low band gap cells is very sensitive to the balance of the charge transport. For a low band gap cell with an active layer thickness of 250 nm, the fill factor of 50% for balanced transport is reduced to less than 40% by an imbalance of only one order of magnitude. © 2011 Wiley Periodicals, Inc.
Topics
charge transportcomputer modelingconducting polymersActive LayerBand gapsBulk heterojunction solar cellsCarrier densityCharge transportcomputer modelingEnhanced absorptionFill factorInterference effectsLow band gapLow bandgap polymersMethoxyMethyl estersOptical parameterOrder of magnitudePhenylenevinyleneRedshiftingSolar cell efficienciesSpace chargesAbsorptionButyric acidComputer simulationConducting polymersConjugated polymersEnergy gapEstersOrganic conductorsSolar cellsHeterojunctions
TNO Identifier
461460
ISSN
08876266
Source
Journal of Polymer Science, Part B: Polymer Physics, 49(10), pp. 708-711.
Pages
708-711
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