Thin Czochralski silicon solar cells based on diamond wire sawing technology

The novel diamond-wire sawing technology has been applied in the wafering of Czochralski (CZ) silicon. It is found that phase transformations take place on the wafer surfaces, associated with a smaller roughness. The wafers sliced by the diamond-wire saw have a greater mechanical strength than those by the conventional cutting process, beneficial for the preparation of thin wafers. With the decrease of silicon wafers, both the transmittance and the reflectance of sunlight increase in the long wavelength range. After fabricated into the solar cells by a standard process, their performances have been investigated. The short-circuit current significantly decreases with the wafer thickness, which is attributed to the reduction of effective light absorption. The open-circuit voltage also reduces to some extent since the surface recombination becomes more and more dominant in the minority carrier lifetime. For the ultrathin wafers with a thickness of 60 μm, an average conversion efficiency of 16.8% can still be achieved for solar cells based on the standard fabrication process in photovoltaic industry.