Temperature and illumination dependent junction transport in CdTe-CdS solar cells

Various electrical and optical techniques have been used to study junction transport mechanisms in CdTe-CdS solar cells. Current density versus voltage (J-V) characteristics were measured at various temperatures under various broad-spectrum illumination intensities, under visible wavelength monochromatic illumination, and under infrared (IR) illumination. The broad-spectrum J-V data was fit to a parallel diode model in order to extract diode parameters. Analysis reveals the existence of two junction transport mechanisms. The first is an intensity-independent recombination process, dominant at high bias levels under low illumination intensity. The second is a tunneling transport mechanism, dominant at low bias levels under high illumination intensities, with an intensity-dependent reverse saturation current. A physical model is presented that explains the observed behavior.