Issue 5, 2012

Enhanced charge separation in organic photovoltaic films doped with ferroelectric dipoles

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.

Graphical abstract: Enhanced charge separation in organic photovoltaic films doped with ferroelectric dipoles

Supplementary files

Article information

Article type
Paper
Submitted
15 Dec 2011
Accepted
22 Feb 2012
First published
23 Feb 2012

Energy Environ. Sci., 2012,5, 7042-7049

Enhanced charge separation in organic photovoltaic films doped with ferroelectric dipoles

K. S. Nalwa, J. A. Carr, R. C. Mahadevapuram, H. K. Kodali, S. Bose, Y. Chen, J. W. Petrich, B. Ganapathysubramanian and S. Chaudhary, Energy Environ. Sci., 2012, 5, 7042 DOI: 10.1039/C2EE03478F

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