Tuning of the electronic bandgap in colloidal quantum dots (CQDs) by changing their size enables the spectral response of CQD-based photodetectors and photovoltaic devices to be tailored. Multi-junction solar cells made from a combination of CQDs of differing sizes and thus bandgaps are a promising means by which to increase the energy harvested from the Sun's broad spectrum. Here, we report the first CQD tandem solar cells using the size-effect tuning of a single CQD material, PbS. We use a graded recombination layer to provide a progression of work functions from the hole-accepting electrode in the bottom cell to the electron-accepting electrode in the top cell, allowing matched electron and hole currents to meet and recombine. Our tandem solar cell has an open-circuit voltage of 1.06Â V, equal to the sum of the two constituent single-junction devices, and a solar power conversion efficiency of up to 4.2%. © 2011 Macmillan Publishers Limited. All rights reserved.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-11-009-21
Acknowledgements: This publication is based in part on work supported by an award (no. KUS-11-009-21) made by King Abdullah University of Science and Technology (KAUST), by the Ontario Research Fund Research Excellent Program, by the Natural Sciences and Engineering Research Council (NSERC) of Canada, Angstrom Engineering and Innovative Technology. The authors would like to acknowledge the assistance of M. Greiner and A. Fischer for UPS/XPS measurements and discussions. X.W. was partially supported by an Ontario Post Doctoral Fellowship from the Ontario Ministry of Research and Innovation. G.I.K. was partially supported by NSERC. The electron microscopy described in Supplementary Section S11 was performed at the Canadian Centre for Electron Microscopy, which is supported by NSERC and other government agencies.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.