Bosch, ISFH produce 22.1% efficient c-Si solar PV cell

28/08/2013

Bosch Solar Energy (Arnstadt, Germany) and the Institute for Solar Energy Research Hamelin (ISFH, Emmerthal, Germany) have produced a 22.1% efficient crystalline silicon (c-Si) solar photovoltaic (PV) cell using ion implanted interdigitated back junction back contact (IBC) technology.

This is a results of Bosch SE and ISFH's joint development program with IBC technology. The psuedosquare 156mm square PV cell has achieved an output of 5.32 watts peak, the highest value reported for a single junction silicon PV cell, and the organizations expect to realize even higher output with the technology.

Bosch and ISFH note that the cell was produced using industrial processes

“IBC cells are an attractive concept for a future cell generation since optical shading losses due to front-side metalization are avoided and the rear-side metalization can be completely silver-free,” note Bosch SE and ISFH in a press statement.

“By application of novel and smart module interconnection concepts the prominent advantages of an IBC-cell are fully exploited: high voltage, extraordinarily high current density and nice appearance.”

Ion implantation to simplify, reduce costs for IBC

Bosch SE and ISFH further note that while the process sequence for IBC cells is complex, ion implantation can offer a significant simplification, as implantation is single-sided and patterning is achieved by inserting shadow masks on the ion beam.

The organizations note that only one high-temperature step is required, and that due to this simplification of the process flow ion implant technology can dramatically reduce IBC cell cost structure.

Industrial processes used

Bosch and ISFH also report that they were able to develop these cells by using standard industrial techniques and tools instead of lab methods. Furthermore, the cell is based on an n-type silicon wafer grown using the standard Czochralski process.

The cell produced 22.1% efficiency with an open circuit voltage of 676mV, a short circuit current density of 51.6mA/cm2 and a 78.5% fill factor. The organizations state that they have identified potential for further improvements of both open circuit voltage and fill factor.

The project was supported by ion implantation manufacturer Applied Materials Inc. (Santa Clara, California, U.S.).

Bosch, ISFH produce 22.1% efficient c-Si solar PV cell

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