Alexander Hauser

15% efficient large area screen printed string ribbon solar cells

Large area solar cells have been processed at the University of Konstanz using a standard industrial type SiN fire-through process on Evergreen Solars String Ribbon multicrystalline silicon material. After optimisation of the screen printing step and emitter sheet resistivity, efficiencies of 15% have been reached on 8/spl times/10 cm/sup 2/ cells almost independent of material bulk resistivity, which was varied between 1-5 /spl Omega/cm. These are the highest large area efficiencies reached on this very promising and cost-effective material using an industrial type process. Cell parameters exhibit a high homogeneity, demonstrating the excellent post-processing material quality. Further improvements within the solar cell process are still possible and could lead to improved results in the near future.

Investigations on hydrogen in silicon by means of lifetime measurements

Various techniques (SIMS, thermal effusion, FTIR) have been suggested for the determination of the diffusion of hydrogen in multicrystalline silicon. However these methods are either laborious or of a minor accuracy. Our work concentrates on the determination of hydrogen passivation depths in mc-Si by determining the minority carrier lifetime as a function of hydrogen passivation time. For the investigations EMC silicon and reference FZ silicon wafers have been used. From experimental data the passivation depth is obtained numerically using the simulation software PC1D and analytically using a simplified equation. For EMC, passivation depths in regions of good and poor quality have been obtained indicating no significant influence on the passivation depth. Further experiments by polishing the wafer prior to lifetime measurements with a small angle have been performed for determination of the SRV.