N-type boron emitter solar cells with implantation industrial process

The use of ion implantation for PV application could be an innovative way of developing advanced cell structures with respect to a very simple fabrication process. Its application on p-type silicon solar cells has already showed its potential with the achievement of efficiency above 19% with selective emitter structure [1]. Nevertheless, the development of more complexes architectures like the n-type boron emitter is even more promising as the fabrication process would remain simple and the cell efficiency could be significantly improved. This study is dedicated to the achievement of high quality boron implanted emitter on textured surface. Very low emitter saturation current densities (J
_0e
) of 80fA/cm
²
with implied Voc of 665mV were reached. The influence of the thermal treatment was also investigated for P-implantation. Large area solar cells (148.6cm
²
) on n-type Cz substrates were fabricated by co-annealing boron emitter and phosphorous BSF respectively at the front and back side of the cell. This fabrication process only requires nine processing steps which lead to a much simpler process than the conventional one made by means of single side gas diffusion. Finally, efficiencies of 16.9% were obtained with relatively poor open-circuit voltage and short-circuit current. Detailed characterization indicates a poor emitter quality which is not consistent with the saturation current density obtained on symmetrical samples. The impact of the thermal budget on the electrical properties of the wafers was investigated.