Pulsed LED illuminator for carrier lifetime investigation

One of the key parameters of silicon base crystals that affect the solar cells efficiency is a minority charge carriers (MCC) lifetime. A common method of MCC lifetime investigation is open circuit voltage decay time measurement under illumination FEP rectangular light pulses. Earlier we have to implement this MCC parameters investigation method in LED illuminator [1], the main drawback of which was its shape in the form of a spherical segment, limiting the illuminated solar cells area no more than 3 cm × 3 cm. However, recent trends in the photovoltaics are aimed at increasing the area of solar cells that in the case of monocrystalline silicon solar cells reaches 156 mm × 156 mm. In connection with this, it was necessary to improve the existing pulsed LED illuminator in order to increase their illuminated area to the size of modern solar cells. As before, an improved pulsed LED illuminator based on emitting element composed from different colors semiconductor light-emitting diodes, which allows irradiating the sample surface by light with different wavelengths to determine the MCC lifetime at different depths of the silicon base crystal [2].