When 3:30 PM - 5:00 PM Feb 06, 2009
Where 1670 CSE
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Clean Energy: The Case for Thermoelectrics and Photovoltaics

Akram Boukai, University of California - Berkeley

If the entire Arabian Peninsula were a swimming pool of oil 1 meter deep, its oil supply would be exhausted in 600 years at the current rate of oil consumption.  In comparison, the world’s largest oil field, in Saudi Arabia, would be completely depleted of oil in only 2 years, if it were the world’s only source of oil.  Clearly an energy economy that depends solely on oil and coal is not sustainable in the long term especially if global warming concerns are to be believed.  Fortunately, the sun can provide all of earth’s energy needs and has a nearly inexhaustible supply of energy that will endure for over 1.5 billion years.  Thermoelectrics and photovoltaics are able to utilize the sun’s energy and do not pollute.

Thermoelectrics and photovoltaics utilize temperature differences and photons to provide a constant source of DC power respectively.  Their main drawback is their high cost and low efficiency when compared to oil and coal.  In the first part of my talk, I will discuss recent successes we made in increasing the efficiency of a silicon-based thermoelectric device.  We observed a 100-fold improvement in efficiency using silicon nanowires over bulk.  The improvements originate from phonon effects at the nanoscale.  In the second part of my talk, I will discuss our recent work on low cost photovoltaics.  I will show how improvements in the collection of photogenerated carriers will allow for efficient photovoltaics based on metallurgical-grade silicon.  These devices will have comparable efficiencies to those of high-purity silicon photovoltaics but will be cheap as sand figuratively and literally.