At the 37th IEEE Photovoltaic Specialist Conference, which took place in Seattle in June 2011, ISFH and Q-Cells already presented small n-type EWT solar cells with an efficiency of 21.6% and an area of (20 × 20) mm2. The cell process is based on monocrystalline Czochralski n-type silicon.
The novel n-type EWT solar cell with 21% efficiency. Foto: ISFH
The high efficiency EWT solar cell.
The boron-doped emitter is defined with laser structuring and is passivated optimally with an aluminumoxide-siliconnitride double layer. ISFH has now scaled up the solar cell production processes to large wafer formats. A novel back contact design with four busbars has been developed, which reduces the finger length to about 50 mm and makes it possible to realize on this large cell area a metalization with a solar cell resitivity contribution less than 0.5 Ohm·cm2.
The project team at ISFH with project manager Till Brendemühl and the R&D team at Q-Cells SE are particularly pleased with the performance of the best (156 × 156) mm2 area solar cell, which has an efficiency of 21.0%, a Jsc of 40.5 mA/cm2, a Voc of 667 mV, and a fill factor of 77.7%.
“This cell type still has the potential for further improvements. We are confident to reach even higher efficiencies” says physicist Fabian Kiefer, who is developing back-contacted solar cells as part of his PhD thesis.
“Our goal is to simplify the production process significantly, while keeping the efficiencies above 21.0% on large cell area” says Prof. Dr. Nils-Peter Harder, head of the group.
Dr. Roland Goslich | idw
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