Journal
NANO LETTERS
Volume 11, Issue 7, Pages 2955-2961Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nl201472u
Keywords
PbS; MoO3; quantum dot; solar cell; heterojunction; Schottky barrier
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Funding
- Department of Energy
- Fannie and John Hertz Foundation
- National Science Foundation
- Link Foundation
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The ability to engineer interfacial energy offsets in photovoltaic devices is one of the keys to their optimization. Here, we demonstrate that improvements in power conversion efficiency may be attained for ZnO/PbS heterojunction quantum dot photovoltaics through the incorporation of a MoO3 interlayer between the PbS colloidal quantum dot film and the top-contact anode. Through a combination of current-voltage characterization, circuit modeling, Mott-Schottky analysis, and external quantum efficiency measurements performed with bottom- and top-illumination, these enhancements are shown to stem from the elimination of a reverse-bias Schottky diode present at the PbS/anode interface. The incorporation of the high-work-function MoO3 layer pins the Fermi level of the top contact, effectively decoupling the device performance from the work function of the anode and resulting in a high open-circuit voltage (0.59 +/- 0.01 V) for a range of different anode materials. Corresponding increases in short-circuit current and fill factor enable 1.5-fold, 2.3-fold, and 4.5-fold enhancements in photovoltaic device efficiency for gold, silver, and ITO anodes, respectively, and result in a power conversion efficiency of 3.5 +/- 0.4% for a device employing a gold anode.
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