Measurements

Photoelectrical performance measurements of solar cells and small-aperture area concentrator sub-modules with such cells have imposed specific requirements on solar simulating equipment and relevant testing methods. For the accurate indoor measurements, the following procedures with using of the computerized equipment have been developed:

  • spectral response curves in absolute units are recorded for a cell under steady-state colour and modulated monochromatic illumination.
  • illuminated I-V curves are measured by a flash solar simulator with adjustable spectrum.

Two types of installations were designed and manufactured at Photovoltaics Laboratory:

  1. Installation for Spectral Photoresponse and Reflectance Measurements (SPRM-Installation).
  2. Flash Tester for Characterization of the Solar Cells
SPRM-Installation

The Installation is a measuring system for recording the following spectral-dependent parameters of the multi-junction solar cells:

  • Absolute values of the external quantum efficiency (photoresponse);
  • Reflectance coefficients of the mirror-like samples;
  • Optical transmittance of the samples.

The computerized measurements are carried out within wavelength spectral range of λ=350-2000 nm with variable intervals of Δλ=10-50 nm. Photoresponse measurements of the multi-junction (2-, or 3-junction) solar cells are conducted under light bias conditions produced by filtered halogen lamps. Evaluation of the photoresponse in absolute units takes place due to comparison of the photocurrent magnitudes from a calibrated reference cell and the solar cell under test at monochromatic illumination. Reflectance coefficient is obtained due to comparison of the light intensities reflected from a calibrated reference mirror and the sample under test. Monochromatic light modulated by mechanical chopper at f=75 Hz is used in spectral measurements. Digital treatment of the measured analog signals in an electronic unit managed by personal computer is carried out in the Installation. 


Specialized software has been developed for the described SPRM-Installation. This software combines the following functions:

  • Introduction of the initial data about the cell under test (Id, type, structure, area) and the reference cell used in given measurements procedure;
  • Setting the parameters of spectral scanning (initial and final wavelengths, scanning interval);
  • Presentation of all the measured signals as the graphs on wavelength;
  • Construction of the spectral curves in absolute units separately for the different subcells in monolithic structure and for reflectance/transmittance coefficients;
  • Presentation of the summarized spectral graph with the photoresponse curves and the reflectance curve.

 

Flash Tester for Characterization of the Solar Cells

Flash Tester for Characterization of the Solar Cells is a system for I-V curve measurements in solar cells, small-size arrays and concentrator PV submodules. It measures both forward and reverse parts of the I-V characteristics under flash illumination and/or in the dark. A flash is produced by xenon lamp source and allows generating a light pulse controlled for the shape and intensity.


A specialized software has been developed for the described tester. This software includes the following functions: introduction of the initial data about the cell under test (Id, type, structure, area) and the reference cell used in given measurements procedure, measurement resistor magnitude, etc.; provides recording, indication and representation of the I-V curves (both graphically and digitally), control of irradiation intensity, voltage and current wave forms as a function of time, calculation of standard I-V curve parameters (Isc, Voc, Iopt, Vopt, Pmax, FF, Eff.). 

Flash testers can be modified to serve for the different goals: 

Flash tester designed for characterization of concentrator modules 0.5x0.5 m2


Flash tester designed for characterization of flat panels up to 2x3 m2