Community Research and Development Information Service - CORDIS

Roadmap towards 20% cell efficiency

The roadmap discusses two different cell concepts. A screen-printed cell was investigated and possible improvements that can be obtained with input from other workpackages were discussed within the roadmap.

The buried contact cell design was the second considered approach of the roadmap. A detailed loss analysis and comparison of the 17.6% and 18.1% mc-Si efficiency cells has been carried out. The efficiency potential was determined using PC1D modelling, literature information and again input from another worpackage, leading to future possibilities to reach large area mc-Si 20% solar cells.

The loss analysis of the 18.1% solar cell showed that major improvement can be done by replacing the full area aluminium back surface field by a local rear contact scheme that provides low back surface recombination velocity and high optical rear surface reflectivity. Front surface recombination velocity can be lowered by using an additional thin thermal silicon oxid layer underneath the silicon nitride antireflection coating. Fillfactor of the 18.1% cell was 77%. Using a similar plating process, we have previously achieved fill factors of up to 78.8% and a fill factor of 79.0% does not seem unrealistic.

Another high efficiency improvement that may be implemented is the use of the zero-shading loss cell design, the angled buried contact concept. By succesfully applying all improvement the large area mc-Si solar cell this roadmap is leading to has a short circuit current density of 39.6mA/cm2, an open circuit voltage of 642.9 mV and a fillfactor of 79%, resulting in an efficiency of 20,1%.

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