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Charge-extraction strategies for colloidal quantum dot photovoltaics

Abstract

The solar-power conversion efficiencies of colloidal quantum dot solar cells have advanced from sub-1% reported in 2005 to a record value of 8.5% in 2013. Much focus has deservedly been placed on densifying, passivating and crosslinking the colloidal quantum dot solid. Here we review progress in improving charge extraction, achieved by engineering the composition and structure of the electrode materials that contact the colloidal quantum dot film. New classes of structured electrodes have been developed and integrated to form bulk heterojunction devices that enhance photocharge extraction. Control over band offsets, doping and interfacial trap state densities have been essential for achieving improved electrical communication with colloidal quantum dot solids. Quantum junction devices that not only tune the optical absorption spectrum, but also provide inherently matched bands across the interface between p- and n-materials, have proven that charge separation can occur efficiently across an all-quantum-tuned rectifying junction.

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Figure 1: Colloidal quantum dot photovoltaics.
Figure 2: Architectures for depleted bulk heterojunction quantum dot photovoltaics.
Figure 3: Engineering the electronics of the CQD/electrode interface.
Figure 4: The quantum junction solar cell.

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Acknowledgements

The authors acknowledge J. Xu for his contributions to the figures. This publication is based in part on work supported by Award KUS-11-009-21, made by King Abdullah University of Science and Technology (KAUST), the Ontario Research Fund Research Excellence Program, the Natural Sciences and Engineering Research Council (NSERC) of Canada, and Angstrom Engineering and Innovative Technology. X.L. would like to acknowledge a scholarship from the China Scholarship Council (CSC).

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Lan, X., Masala, S. & Sargent, E. Charge-extraction strategies for colloidal quantum dot photovoltaics. Nature Mater 13, 233–240 (2014). https://doi.org/10.1038/nmat3816

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