n the Monday afternoon plenary session on optics a
Post# of 22454
Prior to about 2011, record efficiencies were in the range of 25%. However, that record was broken by Alta Devices by recognizing the importance of luminescent emission, jumping the record efficiency to 28.8%. Two-junction and four-junction efficiency records soon reached 31.5% and 38.8%, respectively, based on this principle.
Yablonovitch argued that while GaAs has been seen as expensive as compared to silicon, it can actually be made very efficient using an epitaxial liftoff process. In fact, he said, GaAs would ultimately be much less expensive than silicon because you would need much less material.
Thermophotovoltaics, he explained is not about the holes and electrons: it's all about the photon management. To recycle the photons, one uses a superb rear reflector that will drive higher efficiencies because GaAs is the most efficient fluorescent material that can be pumped -- with as high as 99.7% luminescent efficiency currently documented.
Using this principle, Yablonovitch showed how the work of his student Patrick Xiao demonstrates that electro-luminescent refrigeration could be possible and used for vaccine storage, and how high-temperature thermophotovoltaiacs could be applied in cars and autonomous vehicles.
http://spie.org/about-spie/press-room/spie-op...s#Emerging