Photon-enhanced thermionic emission for solar concentrator systems.
Solar-energy conversion usually takes one of two forms: the 'quantum' approach, which uses the large per-photon energy of solar radiation to excite electrons, as in photovoltaic cells, or the 'thermal' approach, which uses concentrated sunlight as a thermal-energy source to indirectly produce electricity using a heat engine. Here we present a new concept for solar electricity generation, photon-enhanced thermionic emission, which combines quantum and thermal mechanisms into a single physical process. The device is based on thermionic emission of photoexcited electrons from a semiconductor cathode at high temperature. Temperature-dependent photoemission-yield measurements from GaN show strong evidence for photon-enhanced thermionic emission, and calculated efficiencies for idealized devices can exceed the theoretical limits of single-junction photovoltaic cells. The proposed solar converter would operate at temperatures exceeding 200 degrees C, enabling its waste heat to be used to power a secondary thermal engine, boosting theoretical combined conversion efficiencies above 50%.
Schwede
Jared W
JW
Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California 94305, USA.
Bargatin
Igor
I
Riley
Daniel C
DC
Hardin
Brian E
BE
Rosenthal
Samuel J
SJ
Sun
Yun
Y
Schmitt
Felix
F
Pianetta
Piero
P
Howe
Roger T
RT
Shen
Zhi-Xun
ZX
Melosh
Nicholas A
NA