The effects of monochromatic light modes and filtering systems on the measurement of spectral responsivity of photovoltaic(PV) modules are analyzed. According to the structure characteristics of PV modules, a PV module spectral responsivity measurement device was established based on the steady-state monochrome light source, main bias light source, auxiliary bias light source and phase-locked filter testing system. The nondestructive testing of spectral responsivity of solar cells in PV module was realized. The effects of irradiance of main bias light source, irradiance of auxiliary bias light source and temperature of PV module on spectral responsivity and spectral mismatch factor are analyzed. The influence of different sampling monochrome spot area on the relative spectral response measurement of solar cells under small spot test conditions is analyzed. The spectral responsivity of the PV module slices was tested by using the small spot measurement system. The accuracy of the nondestructive measurement device is verified by comparing the nondestructive test results with the slice measurement results.
GaInP2/InGaAs/Ge triple-junction solar cells have become the main energy source for space on-orbit applications. For the sake of the three composed sub-cells, including GaInP2, InGaAs and Ge sub-cell, the monolithic triple-junction solar cells can make use of solar irradiance in the wavelength range of 300 nm to 1800 nm. Before assembled into space solar arrays, each solar cell’s current-voltage curves should be measured in laboratories on earth by AM0 solar simulators, to know their key parameters especially short circuit current. Solar cell’s current-matching is crucial for assembling into arrays. While spectral responsivity is essential for spectral mismatch factors (MMFs) calculation during the current-voltage measurement. MMF corresponding to each sub-cell should be analyzed, so spectral responsivity of each sub-cell of monolithic solar cell was required to be measured out. But sub-cells are connected in series in a monolithic multijunction solar cell, and current-limiting effect makes traditional spectral responsivity measurement which is suitable for single-junction solar cells not applicable anymore. For measuring the spectral responsivity of monolithic multi-junction solar cells, optimized bias light and bias voltage are required to make the tested target sub-cell be the current-limiting one. The wavelength range and irradiance intensity of the bias light, the direction and value of the bias voltage, should be chose and adjusted appropriately during the measurement, otherwise will lead to measurement artifacts and obtain incorrect results. In this paper, combing optimization of bias light and bias voltage with monochromatic light system, we would present method and detailed procedures for measuring the spectral responsivity of monolithic GaInP2/InGaAs/Ge triple-junction space solar cells.
The effect of current mismatch on IV performance of photovoltaic (PV) module is analyzed. Based on the current mismatch theory of solar cell and the series and parallel relation of each cell in the photovoltaic module, the influence analysis program of the current mismatch caused by the irradiance non-uniformity and the response difference of the solar cells in the PV module is established. The experimental and theoretical verification of the IV curve and the PV curve of a photovoltaic module under different shielding conditions have been carried out. It is found that the theoretical results are in good agreement with the experimental results. The influence of irradiance non-uniformity on the measurement of optoelectronic parameters of photovoltaic modules under the conditions of different position of reference solar cell is analyzed. Through theoretical calculation, it is found that in order to reduce the influence of the current mismatch of solar cells on the photoelectric performance test of the photovoltaic module, the difference of solar cells in the PV module and the irradiance non-uniformity of the sunlight simulator should both be reduced, and the irradiance intensity at the standard solar cell position should be consistent with the average irradiance intensity of the test area.