Optimized high-efficiency silicon solar cells with Jsc=42 mA/cm2 and eta=23.3%

In this paper the recent progress in the development of high-efficiency silicon solar cells at Fraunhofer ISE is reported. By a reduction of shadowing losses and an optimization of the anti-reflection coating the efficiency was improved up to 23.3 % on FZ-Si with an excellent short circuit current of 42 mA/cm2. With the optimized scheme a new record value for Cz-Si has been achieved: 22 %. Since the used high-efficiency process is quite complicated, another task was to simplify the process, while keeping the efficiency on a high level (> 20 %). This goal was reached with the RP-PERC process which is around 3 to 4 times less complex, but still leading to efficiencies up to 21.6 %. In the second part of the paper the influence of corona charges on the surface recombination velocity of lifetime test structures and solar cells was studied. The observed dramatic influence - S varies from 10 cm/s to 3000 cm/s, V(ind OC) from -44 mV to +11 mV - is in very good correlation with theoretical predictions. Especially, a cell with interdigitated rear contact grid was a fruitful instrument for this study. Additionally, this cell type is an excellent bifacial cell with efficiencies of 20.6 % and 19.3 % for illumination from the unmetallized and metallized side, respectively.