Nanosociety Meeting Friday @ 12pm, McCullough 115: Tuning the shape of Semiconductor Nanowires for Advanced Photovoltaics

Jia Zhu (Cui Group) will be presenting his latest research on making  efficient nanostructured amorphous silicon solar cells at 12pm in McCullough 115. Pizza will be served.

Tuning the shape of Semiconductor Nanowires for Advanced Photovoltaics

Jia Zhu

Department of Electrical Engineering

Cui Group

 

Tuning the shape of nanostructures can have a strong effect on photon management and charge carrier collection for photovoltaics. Here we demonstrate two examples of nanowire shape designing: nanocones and branched nanowires.

Compared to uniform diameter nanowires, nanocones have been shown for absorbing light with much reduced reflection due to near perfect impedance match. One step further, we demonstrate a new concept of nanodome solar cells, with nanocone arrays as the center piece of this design. The nanodome solar cells will not only greatly reduce light reflection, but also efficiently couple light into propagating wave, which dramatically enhance light travelling path. This new design provides another approach to decouple the direction of light absorption and charge collection, but with much reduced surface area and material usage, compared to nanowire radial p-n junction structure. Amorphous Si solar cell was used as a demonstration of concept. Nanodome solar cells can absorb 46% more sunlight than flat film devices with the same thickness. We demonstrate nanodome devices with a power efficiency of 5.9%, which is 25% higher than flat film one. This nanodome design can be applied to a variety of other solar cell technologies.

PbSe nanocrystals have shown greatly enhanced multi exciton generation (MEG) effect, one important step toward third generation solar cells. However, it is difficult o extract generated carriers from nanocrystals without good transport pathways. Three dimensional branched nanowire, with strong quantum confinement within two dimensions, and the connected third dimension as an efficient charge carrier pathway, can be ideal for enhanced MEG effect, light absorption, and carrier collection. We demonstrate successfully a large area growth of PbSe Hyperbranced and Chiral Branched Nanowires on a variety of substrates. More interestingly, Chiral Branched Nanowires reveal a new nanowire growth mechanism, dislocation driven growth, which can be applied to a variety of materials.