Exceeding the solar cell Shockley-Queisser limit via thermal up-conversion of low-energy photons
Abstract
Maximum efficiency of ideal single-junction photovoltaic (PV) cells is limited to 33% (for 1 sun illumination) by intrinsic losses such as band edge thermalization, radiative recombination, and inability to absorb below-bandgap photons. This intrinsic thermodynamic limit, named after Shockley and Queisser (S-Q), can be exceeded by utilizing low-energy photons either via their electronic up-conversion or via the thermophotovoltaic (TPV) conversion process. However, electronic up-conversion systems have extremely low efficiencies, and practical temperature considerations limit the operation of TPV converters to the narrow-gap PV cells. Here we develop a conceptual design of a hybrid TPV platform, which exploits thermal up-conversion of low-energy photons and is compatible with conventional silicon PV cells by using spectral and directional selectivity of the up-converter. The hybrid platform offers sunlight-to-electricity conversion efficiency exceeding that imposed by the S-Q limit on the corresponding PV cells across a broad range of bandgap energies, under low optical concentration (1-300 suns), operating temperatures in the range 900-1700 K, and in simple flat panel designs. We demonstrate maximum conversion efficiency of 73% under illumination by non-concentrated sunlight. A detailed analysis of non-ideal hybrid platforms that allows for up to 15% of absorption/re-emission losses yields limiting efficiency value of 45% for Si PV cells.
- Publication:
-
Optics Communications
- Pub Date:
- March 2014
- DOI:
- 10.1016/j.optcom.2013.10.042
- arXiv:
- arXiv:1310.5570
- Bibcode:
- 2014OptCo.314...71B
- Keywords:
-
- Photovoltaics;
- Thermophotovoltaics;
- Solar energy conversion;
- Up-conversion;
- Frequency-selective surfaces;
- Angularly-selective surfaces;
- Physics - Optics;
- Physics - Computational Physics
- E-Print:
- 28 pages, 9 figures