Application of scanning deep level transient spectroscopy for characterisation of multicrystalline silicon

Minority carrier trap levels in cast p-type multicrystalline silicon solar cell material were identified by means of scanning deep level transient spectroscopy. The material was investigated in the as-grown state and after the solar cell process. Additionally iron diffused samples (1050 degrees C), quenched or slow-cooled, were used. Two levels in the as-grown material were detected at E(C)-0.2 eV and E(C)-0.45 eV. The E(C)-0.45 eV level is also found with comparable defect density in the material after the solar cell process and after iron diffusion, respectively. In the quenched samples the iron-boron level at E(C)-0.29 eV is observed. Spatially resolved measurements for the E(C)-0.45 eV level reveal an inhomogeneous defect distribution in the iron diffused and quenched samples which is not related to crystal defects like grain boundaries or dislocations.