Holographic spectrum splitter for ultra-high efficiency photovoltaics
read more
Citations
Optical Holography: Principles, Techniques and Applications
Optimum matching of photovoltaic–thermophotovoltaic cells efficiently utilizing full-spectrum solar energy
One of the most efficient methods to utilize full-spectrum solar energy: A photovoltaic-thermoradiative coupled system
Simulation and partial prototyping of an eight‐junction holographic spectrum-splitting photovoltaic module
Increased Photovoltaic Power Output via Diffractive Spectrum Separation
References
Increased photovoltaic power output via diffractive spectrum separation
A High-Power-Density DC–DC Converter for Distributed PV Architectures
Lateral Spectrum Splitting Concentrator Photovoltaics: Direct Measurement of Component and Submodule Efficiency
Spectral splitting module geometry that utilizes light trapping
Spectrum-splitting photovoltaics: Holographic spectrum splitting in eight-junction, ultra-high efficiency module
Related Papers (5)
A Review of Ultrahigh Efficiency III-V Semiconductor Compound Solar Cells: Multijunction Tandem, Lower Dimensional, Photonic Up/Down Conversion and Plasmonic Nanometallic Structures
Addendum: Tanabe, K. A Review of Ultrahigh Efficiency III-V Semiconductor Compound Solar Cells: Multijunction Tandem, Lower Dimensional, Photonic Up/Down Conversion and Plasmonic Nanometallic Structures. Energies, 2009, 2, 504-530.
Frequently Asked Questions (20)
Q2. What is the effective index of refraction of the DCG gratings?
The effective index of refraction of the DCG gratings is 1.3 while the substrate, commonly fused silica or glass ranges from 1.45 to 1.55.
Q3. What is the output of the grating?
the output intensities and diffraction angles from the final grating are used to determine which underlying solar cell any particular output from the bottommost grating will hit.
Q4. What is the optimum output to the cells?
The optimum output to the cells accounting for both increased concentration and increased loss from the concentrator must be balanced.
Q5. What is the way to model the holographic gratings?
Coupledwave analysis, considering only the input (0th order) and 1st order output is a valid approximation when the angle of incidence is near the Bragg angle and the grating is thick.
Q6. How many diffraction bands can be adduced into a hol?
the index of refraction modulation can vary from 0.01 to up to 0.4, but as this index modulation increases scattering into spurious diffraction orders also increases14, so the authors have restricted the range of search from 0.01 to 0.06.
Q7. What is the effect of the current match?
As the solar input varies over the course of a day or year or with changing location, the current match may no longer hold, decreasing efficiency.
Q8. What is the angular sensitivity of diffractive optics?
Since using angle-of-incidence sensitive diffractive optics requires tracking of the sun and use of only the light in the direct solar spectrum rather than the global solar spectrum, concentration allows both a compensation for the diffuse light lost as well as the potential to access much higher overall efficiencies.
Q9. How many photons are hitting each of the four tandem cells?
The total output fraction of input light intensity hitting each cell can be converted to a photon flux using the AM1.5d spectrum to determine how many above bandgap photons are hitting each of the four tandem cells.
Q10. What is the optimum amount of absorber materials?
However since the lattice constants of epitaxially grown layers must be the same or similar to maintain high material quality and minimize defects, there are limits to the number of absorber materials that can be incorporated.
Q11. What is the spectral band of the gratings?
Each of the three diffraction gratings diffracts one spectral band into its first diffracted order toward the cell it is intended for and a fourth band of light passes straight through the three holographic gratings (in their zeroth order) to the cell directly underneath.
Q12. What is the angle of incidence of light?
As the wavelength deviates slightly from the design wavelength, so too does the angle corresponding to the output diffraction order shift slightly.
Q13. What is the angular sensitivity of the CPC?
In the concentration scheme used for the holographic splitter (Fig. 2), the top CPC is a curved, silvered mirror, which concentrates light orthogonal to the direction of spectral splitting.
Q14. What are the de-rating factors for holograms?
These de-rating factors account for losses such as non-radiative recombination and parasitic absorption and produce realistic cell efficiency estimates from the theoretical detailed balance calculation.
Q15. What is the optimum bandgap material for solar cells?
Thus using higher bandgap materials to collect higher energy photons returns more electrical energy upon absorption and collection.
Q16. how much efficiency is the holographic spectrum splitter?
Estimated system efficiency accounting for realistic cell performance and other losses is 36.14%, matching current records for lateral spectral splitting, with the potential for much higher efficiency upon future design iteration.
Q17. What is the GCWA method used to model the holographic spectrum splitter?
To model the full compound holographic spectrum splitter, the output of each successive grating in a particular stack is found using GCWA for normally incident light.
Q18. What is the effect of the grating on the diffraction efficiency?
Holographic diffraction gratings have a decrease in diffraction efficiency as the wavelength deviates from this design wavelength as shown in Figure 1.
Q19. What is the optimum spectral efficiency of the holograms?
They have a combined de-rated detailed balance efficiency of 46.97% using these de-rated parameters of 90% absorption, 1% ERE for unconcentrated illumination and perfect spectral splitting.
Q20. What is the trade-off between holographic materials and available substrates?
This trade-off also incentivizes the use of holographic materials which can be better index-matched to available substrates and which do not require post-processing which might alter their pre- and post-recording properties.