Dr. Ted Sargent’s reviewin Nature outlines the challenges and opportunities for solution-processed photovoltaics. Demand for expensive high-efficiency photovoltaic cells at prices competitive with legacy energy supplies persists against a backdrop of emerging less costly and less efficient polysilicon-based cells. Solar photovoltaics faces a critical challenge – much of the sun’s energy is lost to heat and true breakthroughs in efficiencies will likely require capturing the sun’s infrared light in addition to the visible component. Colloidal quantum-dot solar cells, processed in solution, are comparably much morecost-effective to manufacture and offer the opportunity to integration multiple junctions capturing the infrared spectrum.
Quantum dots are nanoscale semiconductor particles that can be tuned to absorb different parts of the sun’s spectrum based on their size; they also allow multiple exciton generation from a single photon. In a review in Nature (2012), Sargent and distinguished co-authors outlined the state of the art materials interface engineering at work in solution-processed photovoltaics including (1) dye-sensitized solr cells (2) organic photovoltaics (3) solution-processed bulk inorganic solar cells, and (4) colloidal quantum-dot solar cells. The Sargent group was the first to demonstrate quantum dot solar cells that could achieve infrared light harvesting. The landmark study is regularly cited since it first appeared in Nature Materials in 2005 and is responsible for a surge in research world-wide into this new type of inexpensive colloidal solar cell. In 2012, Dr. Sargent and his group reported in Nature Nanotechnology the highest certified solar efficiency (7%) using colloidal quantum dots. In parallel, the group demonstrated the first colloidal quantum dot tandem solar cell employing multiple light-harvesting junctions (Nature Photonics, 2011); and the first device to exploit the quantum size effect to direct the flow of charge carriers inside the active layer, a concept termed quantum funneling (Nano Letters, 2011). Ted Sargent is a Professor in the Edward S. Rogers Sr. Department of Electrical and Computer Engineering at the University of Toronto, and Canada Research Chair in Nanotechnology. He received the B.Sc.Eng (Engineering Physics) from Queen’s University in 1995, and the Ph.D. in Electrical and Computer Engineering (Photonics) from the University of Toronto in 1998. His research has been published in Nature, Nature Materials, Nature Photonics, and Nano Letters. His 2005 book The Dance of Molecules: How Nanotechnology is Changing Our Lives (Penguin) has been translated into French, Spanish, Italian, Korean, and Arabic. More about Dr. Sargent and his research: http://www.light.utoronto.ca/