An optimal driving force for converting excitons into free carriers in excitonic solar cells

David C. Coffey; Bryon W. Larson; Alexander W. Hains; James B. Whitaker; Nikos Kopidakis; Olga V. Boltalina; Steven H. Strauss; Garry Rumbles

doi:10.1021/jp302275z

An optimal driving force for converting excitons into free carriers in excitonic solar cells

David C. Coffey, Bryon W. Larson, Alexander W. Hains, James B. Whitaker, Nikos Kopidakis, Olga V. Boltalina, Steven H. Strauss, Garry Rumbles^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

149 Citations (Scopus)

Abstract

A general but limiting characteristic in excitonic photovoltaics is that a portion of the incident photon energy appears necessary for converting excitons into electrical charges, resulting in a loss of efficiency. Currently, the mechanism underlying this process is unclear. Here, we describe the development of an experimental method for measuring charge creation yields in organic solar cell materials. We use this method to examine a series of conjugated polymer:fullerene blend films and observe two unexpected features: the existence of an optimal driving force and a loss in conversion efficiency if this force is exceeded. These observations have implications for the design of excitonic photovoltaic devices and can be explained by a simple Marcus formulation that introduces the importance of reorganization energy.

Original language	English
Pages (from-to)	8916-8923
Number of pages	8
Journal	Journal of Physical Chemistry C
Volume	116
Issue number	16
DOIs	https://doi.org/10.1021/jp302275z
Publication status	Published - 26 Apr 2012
Externally published	Yes

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abstract = "A general but limiting characteristic in excitonic photovoltaics is that a portion of the incident photon energy appears necessary for converting excitons into electrical charges, resulting in a loss of efficiency. Currently, the mechanism underlying this process is unclear. Here, we describe the development of an experimental method for measuring charge creation yields in organic solar cell materials. We use this method to examine a series of conjugated polymer:fullerene blend films and observe two unexpected features: the existence of an optimal driving force and a loss in conversion efficiency if this force is exceeded. These observations have implications for the design of excitonic photovoltaic devices and can be explained by a simple Marcus formulation that introduces the importance of reorganization energy.",

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AU - Hains, Alexander W.

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AU - Kopidakis, Nikos

AU - Boltalina, Olga V.

AU - Strauss, Steven H.

AU - Rumbles, Garry

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AB - A general but limiting characteristic in excitonic photovoltaics is that a portion of the incident photon energy appears necessary for converting excitons into electrical charges, resulting in a loss of efficiency. Currently, the mechanism underlying this process is unclear. Here, we describe the development of an experimental method for measuring charge creation yields in organic solar cell materials. We use this method to examine a series of conjugated polymer:fullerene blend films and observe two unexpected features: the existence of an optimal driving force and a loss in conversion efficiency if this force is exceeded. These observations have implications for the design of excitonic photovoltaic devices and can be explained by a simple Marcus formulation that introduces the importance of reorganization energy.

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An optimal driving force for converting excitons into free carriers in excitonic solar cells

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