Parasitic Shunt Losses in All-Side SiNx Passivated mc-Si Solar Cells

In search of solar cell concepts that allow processing thinner wafers (alt;150 micron), the conventional full Al rear side is replaced by an open rear metallization combined with a dielectric passivation layer. We show a gain of 2.1% (relative) in the product of J?Ƴc?Voc, when we apply a passivated SiNx dielectric layer and local Al contacts on the rear of p-type mc-Si solar cells instead of a full Al-BSF. To achieve this gain, metallization designs of H-patterns and point-contacts were used with a rear coverage less than 8%. The gain in J?Ƴc?Voc is an improvement over our previously reported results for open rear side cells with rear coverage of 14%. In addition, we propose a new method to quantify parasitic shunting to evaluate the efficiency potential of this cell concept. Experimental evidence shows that the parasitic shunting is one of the main limiting factors and the new method predicts a gain in Jsc and Voc in absence of this phenomenon. Omitting additional resistive losses of the open rear side cell compared to its full-coverage counterpart, we predict a gain in efficiency of about 0.5% absolute if parasitic shunting could be eliminated.