Influence of high-temperature processes on multicrystalline silicon

Several combinations of oxidation and phosphorus diffusion processes suitable for silicon solar cell processing were applied to solar grade multicrystalline silicon. This resulted in drastic changes of the minority carrier lifetime. The effect of extended light exposure of the samples was measured with injection level dependent lifetime spectroscopy. This revealed iron as a contaminant source present in non-treated samples which could significantly be reduced by an appropriate phosphorus diffusion. To monitor the changes with a high spatial resolution the Carrier Density Imaging (CDI) technique was applied showing distinct differences between oxidations and diffusions.