Extended spectral analysis of internal quantum efficiency

A powerful new method for identifying the performance-limiting mechanisms in silicon solar cells has been developed and tested at Sandia. This method uses the internal quantum efficiency (IQE) of the device at both near-infrared and near-bandgap wavelengths. The conventional interpretation of IQE is expanded to accommodate textured surfaces and long diffusion lengths, and extended to near-bandgap wavelengths where internal optical effects play an important role. This paper describes how the information available from this extended analysis can be used to obtain a value for the internal optical reflectance of the back surface, and to separate the effects of diffusion length from back-surface recombination. Results from experimental tests verify the method. The information obtained can be used to compute recombination components for the cell, and to quantify the light-trapping effectiveness of the device