Sol-gel Synthesized Dielectric Films as a Diffusion Barrier to Rear Side Contact Metal

Abstract It is essential to mitigate the costs of cell production in order to achieve an increasing share of the industrial manufacture of advanced and more efficient solar cells. This work aims to contribute to the efficiency enhancement and cost reduction of rear contact cells, such as passivated emitter rear contact (PERC) cells. In order to realize these goals, various dielectric materials are proposed that mainly function as a diffusion barrier to the rear contact metal, i.e. aluminum as well as impurities. Dielectric materials that are formulated as chemical solutions are coated on single-side-polished, monocrystalline silicon. Their barrier function is tested with three different screen-printable aluminum pastes. Among various materials, five inks showed an absolute barrier behavior against different aluminum pastes. Furthermore, the compatibility of these materials with the existing passivation layer, ALD-AlOx, (AlOx film deposited by atomic layer deposition) is imaged by photoluminescence spectroscopy. The minimum film thickness that is necessary for preventing aluminum penetration is determined by scanning electron microscopy (SEM) and ellipsometry. This is found to be 450 nm for the cured dielectric material that showed the best overall results.