Journal
ENERGY & ENVIRONMENTAL SCIENCE
Volume 5, Issue 5, Pages 7042-7049Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c2ee03478f
Keywords
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Funding
- National Science Foundation [ECCS-1055930]
- Institute of Physical Research and Technology, Iowa State University
- U.S. Department of Energy, Office of Basic Energy Sciences, through the Ames Laboratory
- U.S. Department of Energy [DE-AC02-07CH11358]
- Iowa Power Fund
- Div Of Electrical, Commun & Cyber Sys
- Directorate For Engineering [1055930] Funding Source: National Science Foundation
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A key requirement for realizing efficient organic photovoltaic (OPV) cells is the dissociation of photogenerated electron-hole pairs (singlet-excitons) in the donor polymer, and charge-transfer-excitons at the donor-acceptor interface. However, in modern OPVs, these excitons are typically not sufficiently harnessed due to their high binding energy. Here, we show that doping the OPV active-layers with a ferroelectric polymer leads to localized enhancements of electric field, which in turn leads to more efficient dissociation of singlet-excitons and charge-transfer-excitons. Bulk-heterojunction OPVs based on poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester are fabricated. Upon incorporating a ferroelectric polymer as additive in the active-layer, power conversion efficiencies increase by nearly 50%, and internal quantum efficiencies approach 100%-indicating complete exciton dissociation at certain photon energies. Similar enhancements in bilayer-heterojunctions, and direct influence of ferroelectric poling on device behavior show that improved dissociation is due to ferroelectric dipoles rather than any morphological change. Enhanced singlet-exciton dissociation is also revealed by photoluminescence lifetime measurements, and predicted by simulations using a numerical device model.
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