Crystalline silicon solar cells are at this moment predominantly made from p-type silicon wafers. Researchers at ECN have shown that significantly higher efficiencies can be obtained by making the solar cells from n-type silicon wafers. They used process steps, such as screen printing, of the same low-cost character as are presently used in mainstream industrial production.
A major breakthrough that the researchers obtained was a novel method (patented) for passivating the emitter of their n-type solar cells. This novel method increases the efficiency of these cells significantly over the values obtained for p-type ones, when using cell processes of comparable cost and simplicity. For single-crystalline silicon the advantage is of order 1% absolute (determined in an in-house comparison at ECN); for multicrystalline silicon the gain depends on the quality of the silicon wafer.
A best efficiency of 18.3% on single crystalline Czochralski wafers (17.9% average), and 16.4% on multicrystalline silicon was demonstrated, using standard industrial wafers of 125mm size in both cases.
Since the new cell process can be carried out using the same manufacturing equipment as the p-type cell process, it will allow rapid implementation, possibly even by modifying existing process lines. Together with other advantages and improvements based on this new cell process, low-cost screen printed n-type cells are potentially capable of becoming a strong new technology in the PV market. ECN intends to further develop and bring to commercialization several solar cell types based on this technology on short and medium time frames.