For Quantum Dot Solar Cells, Size Makes All the Difference

27 May, 2014

Solar energy is all about efficiency. To challenge fossil fuels, solar cells must convert more sunshine into electricity, at lower cost, than they can do today. Tiny particles of lead and sulfur called PbS quantum dots (QDs) show potential as solar cell components because, among other attributes, they are simple to produce and absorb sunlight well. But to optimize efficiency, researchers need to better understand how PbS QDs interact with sunlight to produce electrons.
Omar Mohammed and colleagues add a piece to the puzzle with a careful investigation into how light affects electrons at the space between PbS QDs and another material commonly used in solar cells (DOI: 10.1021/ja413254g).
The researchers find that the dots’ size distribution is critical. Their size determines not only what wavelength of light the QDs will absorb but also how quickly that light produces work-ready electrons at the interface. With careful size control, researchers can tune PbS QDs to inject charge carriers into the surrounding material ultrafast, not at all, and every speed in between. Such information is essential to the design of solar-based devices if researchers hope to increase efficiency with quantum dots.
Jenny Morber, Ph.D