Terrestrial photovoltaic power systems with sunlight concentration

Several concentrator solar cells were tested with efficiencies approaching 20%. Trends in concentrator cell design continue toward smaller devices, reducing the total current generation per cell and reducing internal dissipation through series resistance. Concentrator cells of various thickness, but otherwise identical processing were tested, and as would be expected for silicon devices, one sun short circuit current increased with thickness. Peak efficiency also increased with thickness, but high irradiance performance was often better for thinner cells because of the decreased series resistance of the base region. Use of a properly calibrated and matched reference cell reduces measurement error caused by changes in the solar spectrum. Error due to spectral response mismatch between the test cell and reference cell can be quantified using a spectral mismatch parameter described. Reference cell calibration techniques currently in use include uncertainty due to the range of solar spectra permitted during calibration. A calibration technique is presented that eliminates this source of calibration error through the use of a tabular spectrum.