Enhanced charge separation in organic photovoltaic films doped with ferroelectric dipoles

TitleEnhanced charge separation in organic photovoltaic films doped with ferroelectric dipoles
Publication TypeJournal Article
Year of Publication2012
AuthorsNalwa KS, Carr JA, Mahadevapuram RC, Kodali HK, Bose S, Chen YQ, Petrich JW, Ganapathysubramanian B, Chaudhary S
Journal TitleEnergy & Environmental Science
Volume5
Pages7042-7049
Date Published05
Type of ArticleArticle
ISBN Number1754-5692
Accession NumberWOS:000303251500046
Keywordsefficiency enhancement, MORPHOLOGY, open-circuit voltage, polymer solar-cells, transistors
Abstract

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.

URL<Go to ISI>://WOS:000303251500046
DOI10.1039/c2ee03478f
Alternate JournalEnergy Environ. Sci.