Journal
ACS NANO
Volume 9, Issue 8, Pages 8321-8334Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.5b02853
Keywords
charge transfer; SILAR; lead sulfide; titanium dioxide; quantum dot; surface coverage; nanostructured solar cells
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Funding
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-SC0001060]
- U.S. Department of Energy through the Bay Area Photovoltaic Consortium [DE-EE0004946]
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The power conversion efficiency of quantum-dot-sensitized solar cells (QDSSCs) hinges on interfacial charge transfer. Increasing quantum dot (QD) loading on the TiO2 anode has been proposed as a means to block recombination of electrons in the TiO2 to the hole transport material; however, it is not known whether a corresponding increase in QD-mediated recombination processes might lead to an overall higher rate of recombination. In this work, a 3-fold increase in PbS QD loading was achieved by the addition of an aqueous base to negatively charge the TiO2 surface during Pb cation deposition. Increased QD loading improved QDSSC device efficiencies through both increased light absorption and an overall reduction in recombination. Unexpectedly, we also found increased QD size had the detrimental effect of increasing recombination. Kinetic modeling of the effect of QD size on interfacial charge transfer processes provided qualitative agreement with the observed variation in recombination lifetimes. These results demonstrate a robust method of improving QD loading, identify the specific mechanisms by which increased QD deposition impacts device performance, and provide a framework for future efforts optimizing the device architecture of QDSSCs.
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