The role of defects in solar cells: Control and detection defects in solar cells

The performance of commercial solar cells is strongly controlled by the impurities and defects present in the substrates. Defects induce deep energy levels in the semiconductor bandgap, which degrade the carrier lifetime and quantum efficiency of solar cells. A comprehensive knowledge of the properties of defects require electrical characterization techniques providing information about the defect concentration, spatial distribution and physical origin. The experimental techniques available in our laboratory are described in this work. In contrast, the efficiency of single junction solar cells can be drastically improved by the formation of an intermediate band in the midgap of a semiconductor. The intermediate band can be created from deep level defects if their concentration is high enough. Experimental results proving the intermediate band formation are also presented in this work.