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Organic and nano-structured composite photovoltaics: An overview

Published online by Cambridge University Press:  01 December 2005

Sophie E. Gledhill ,
Brian Scott  and
Brian A. Gregg
Sophie E. Gledhill*
Affiliation:
National Renewable Energy Laboratory, Golden, Colorado 80401
Brian Scott
Affiliation:
National Renewable Energy Laboratory, Golden, Colorado 80401
Brian A. Gregg
Affiliation:
National Renewable Energy Laboratory, Golden, Colorado 80401
*
a) Address all correspondence to this author. e-mail: sophie_gledhill@nrel.go
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Abstract

Organic photovoltaic devices are poised to fill the low-cost, low power niche in the solar cell market. Recently measured efficiencies of solid-state organic cells are nudging 5% while Grätzel’s more established dye-sensitized solar cell technology is more than double this. A fundamental understanding of the excitonic nature of organic materials is an essential backbone for device engineering. Bound electron-hole pairs, “excitons,” are formed in organic semiconductors on photo-absorption. In the organic solar cell, the exciton must diffuse to the donor–accepter interface for simultaneous charge generation and separation. This interface is critical as the concentration of charge carriers is high and recombination here is higher than in the bulk. Nanostructured engineering of the interface has been utilized to maximize organic materials properties, namely to compensate the poor exciton diffusion lengths and lower mobilities. Excitonic solar cells have different limitations on their open-circuit photo-voltages due to these high interfacial charge carrier concentrations, and their behavior cannot be interpreted as if they were conventional solar cells. This article briefly reviews some of the differences between excitonic organic solar cells and conventional inorganic solar cells and highlights some of the technical strategies used in this rapidly progressing field, whose ultimate aim is for organic solar cells to be a commercial reality.

Keywords

NanoscaleOrganicPhotoconductivity
Type
Reviews—Energy and The Environment Special Section
Information
Journal of Materials Research , Volume 20 , Issue 12 , December 2005 , pp. 3167 - 3179
Copyright
Copyright © Materials Research Society 2005

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