EECS Colloquium

Wednesday, August 30, 2023

306 Soda Hall (HP Auditorium)
4:00 – 5:00 pm

Eli Yablonovitch

Professor Emeritus, EECS
Professor in the Graduate School
UC Berkeley


Eli Yablonovitch speaks on "Carbon Negative Technology to Solve the Climate Crisis" (8/30/23)


In 1977, the physicist Freeman Dyson proposed the burial of biomass, as a scalable, economical solution to the CO2 problem.  Today we know that the harvested vegetation should be buried in an engineered dry biolandfill.  Plant biomass can be preserved for thousands of years by burial in a dry environment with sufficiently low thermodynamic “Water Activity”, which is the relative humidity in equilibrium with the biomass.  A “Water Activity” <60% will not support life, suppressing anaerobic organisms, thus preserving the biomass for millennia.  Current agriculture costs, and biolandfill costs, indicate US$60/tonne of sequestered CO2 which corresponds to $0.53/gallon of gasoline.  If scaled to the level of a major crop, existing CO2 can be extracted from the atmosphere and sequester a significant fraction of prior years’ CO2 emissions.


Prof. Yablonovitch introduced the idea that strained semiconductor lasers could have superior performance due to reduced valence band (hole) effective mass. With almost every human interaction with the internet, optical telecommunication occurs by strained semiconductor lasers. He is regarded as a Father of the Photonic BandGap concept, and he coined the term “Photonic Crystal”. The geometrical structure of the first experimentally realized Photonic bandgap is sometimes called “Yablonovite”. In his photovoltaic research, Yablonovitch introduced the 4(n squared) (“Yablonovitch Limit”) light-trapping factor that is in worldwide use, for almost all commercial solar panels. His mantra that “a great solar cell also needs to be a great LED”, is the basis of the world record solar cells: single-junction 29.1% efficiency; dual-junction 31.5%; quadruple-junction 38.8% efficiency; all at 1 sun.


Video of This Presentation