Apparatus and method to characterize multijunction photovoltaic solar cells

1. An apparatus to characterize a multijunction solar cell, the apparatus comprising:

a light-control system to effect a control of an intensity of one or more light beams illuminating the multijunction solar cell, the multijunction solar cell having a plurality of subcells, each subcell having associated thereto a subcell spectral range, each subcell to absorb light at wavelengths comprised within its subcell spectral range, the control of the intensity of the one or more light beams to vary a light intensity in the subcell spectral range of a particular subcell, to obtain varied light intensities, while maintaining substantially constant the light intensity in the subcell spectral ranges of the other subcells;

an electrical characterization system to connect electrically to the multijunction solar cell, the electrical characterization system to measure, for each of the varied intensities, current flowing through the multijunction solar cell as a function of voltage applied to the multijunction solar cell; and

a processing module to process current and voltage data associated to the varied intensities, to obtain processed data, the processed data to determine one more parameters of the particular subcell.

2. The apparatus of claim 1 wherein the light-control system comprises a series of optical filters, each optical filter to transmit one of the one or more light beams at a respective transmission intensity corresponding to one of the varied intensities.

3. The apparatus of claim 1 wherein:

the one or more light beams consists of one light beam;

the light-control system has a plurality of optical filters; and

each optical filter is to filter the one light beam to produce one of the varied light intensities.

4. The apparatus of claim 3 wherein the optical filters include reflection optical filters.

5. The apparatus of claim 1 wherein the one or more light beams has two or more light beams, the light control system having:

a plurality of optical filters, each optical filter to filter one of the two or more light beams to produce one of the varied light intensities; and

an optical beam combiner system to combine the two or more light beams, to obtain a combined light beam, and to provide the combined light beam to the multijunction solar cell.

6. The apparatus of claim 5 wherein the two or more light beams consist of as many light beams as there are subcells in the multijunction solar cell.

7. The apparatus of claim 5 wherein the light control system further has beam-forming optics to form the two or more light beams.

8. The apparatus of claim 7 wherein the beam-forming optics is to form the two of more light beams from light emitted from a single light source.

9. The apparatus of claim 8 wherein the single light source is the Sun.

10. The apparatus of claim 7 wherein the beam-forming optics is to form the two or more light beams from two or more respective light sources.

11. The apparatus of claim 1 wherein the one or more parameters include at least one of an open circuit voltage, a short-circuit current, a maximum power voltage, a shunt resistance, and a fill-factor.

12. An apparatus to characterize a multijunction solar cell, the apparatus comprising:

a light-control system to effect a control of an intensity of one or more light beams illuminating the multijunction solar cell, the multijunction solar cell having a plurality of subcells, each subcell having associated thereto a subcell spectral range, each subcell to absorb light at wavelengths comprised within its subcell spectral range, the control of the intensity of the one or more light beams to vary a light intensity in the subcell spectral range of a particular subcell, to obtain varied light intensities that each produce a varied electrical current in the particular subcell, while maintaining substantially constant the light intensity in the subcell spectral ranges of the other subcells;

an electrical characterization system to connect electrically to the multijunction solar cell, the electrical characterization system to measure, for each of the varied intensities, current flowing through the multijunction solar cell as a function of voltage applied to the multijunction solar cell; and

a processing module to process current and voltage data associated to the varied intensities, to obtain processed data, the processed data to determine one more parameters of the particular subcell.