Exceeding the Shockley-Queisser limit via thermal upconversion of low-energy photons

A talk given by Svetlana V. Boriskina at MRS Fall 2012 Meeting in Boston, MA Abstract:
It has been known for over half a century that the efficiency of even ideal single-junction photovoltaic cells that absorb all the incoming solar radiation is limited to 31% (for one sun illumination) by intrinsic losses such as band edge thermalization and radiative recombination. Approaches to exceed this intrinsic thermodynamic limit, named after Shockley and Queisser, included using concentrated sunlight, engineering multiple-junction and intermediate-band solar cells, exploiting mechanisms of electronic up- and down-conversion of photons, thermophotovoltaic, and thermophotonic. The resulting limiting efficiency can e.g. reach 72% in the case of 36-junction solar cell under illumination by a 1000-times concentrated sunlight.  We will present a fundamentally new approach to exceeding the Shockley-Queisser limit, which is based on the mechanism of thermal upconversion of photons.  We will demonstrate that the limiting intrinsic efficiency of an ideal single-junction solar cell can be increased up to 73% under illumination by an unconcentrated sunlight. A more detailed analysis of non-ideal solar cells that allows for up to 15% of absorption/re-emission losses yields limiting efficiency values exceeding 44%. Finally, we will discuss practical device realizations of the proposed theoretical scheme. Acknowledgment: This work is supported as part of the 'Solid State Solar-Thermal Energy Conversion Center (S3TEC)', an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number: DE-SC0001299/DE-FG02-09ER46577. Slides can also be downloaded here:
Sides in pdf:  www.bio-page.org/boriskina/Boriskina_MRS_Fall2012_Thermal Upconversion.pdf
Powerpoint show: www.bio-page.org/boriskina/Boriskina_MRS_Fall2012_Thermal Upconversion.pps
Movie: www.bio-page.org/boriskina/Boriskina_MRS_Fall2012_Thermal Upconversion.wmv