Improved current extraction from ZnO/PbS quantum dot heterojunction photovoltaics using a MoO3 interfacial layer
Patrick R Brown1, Richard R Lunt, Ni Zhao
1Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Nano Letters
|June 14, 2011
Summary
Adding a molybdenum trioxide (MoO3) interlayer to ZnO/PbS quantum dot solar cells significantly boosts power conversion efficiency. This modification eliminates a performance-limiting Schottky diode, enhancing device stability and output.
Area of Science:
- Materials Science
- Nanotechnology
- Photovoltaics
Background:
- Optimizing photovoltaic devices relies on engineering interfacial energy offsets.
- ZnO/PbS heterojunction quantum dot solar cells offer potential for efficient energy conversion.
- Interfacial properties significantly impact the performance of colloidal quantum dot photovoltaics.
Purpose of the Study:
- To improve power conversion efficiency in ZnO/PbS heterojunction quantum dot photovoltaics.
- To investigate the effect of incorporating a molybdenum trioxide (MoO3) interlayer.
- To understand the mechanism behind efficiency enhancements at the PbS/anode interface.
Main Methods:
- Fabrication of ZnO/PbS quantum dot solar cells with a MoO3 interlayer.
- Current-voltage characterization and circuit modeling.
- Mott-Schottky analysis and external quantum efficiency measurements (bottom- and top-illumination).
Main Results:
- The MoO3 interlayer eliminated a reverse-bias Schottky diode at the PbS/anode interface.
- A high open-circuit voltage (0.59 ± 0.01 V) was achieved, independent of anode material.
- Significant efficiency enhancements were observed for gold (1.5-fold), silver (2.3-fold), and ITO (4.5-fold) anodes, reaching 3.5 ± 0.4% with gold.
Conclusions:
- Incorporating a MoO3 interlayer is an effective strategy for optimizing ZnO/PbS quantum dot photovoltaics.
- The high-work-function MoO3 layer pins the Fermi level, decoupling device performance from anode work function.
- This approach leads to substantial improvements in power conversion efficiency and device stability.
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