A new approach for forming device contacts with improved surface passivation [solar cells]

Increased interest in renewable energy sources and concern for the environment are giving impetus to the search for viable energy alternatives. One step to increasing the economic viability of PV technology is to improve the energy conversion efficiency. Most commercially produced solar cells suffer from poor rear surface passivation, including the buried contact solar cell (BCSC), with a poor back surface field (BSF) produced by an aluminium alloying process. In this work, the low temperature process of metal mediated epitaxial growth (MMEG) is used to produce an improved back surface field (BSF) and surface passivation for the BCSC in conjunction with reduced area contacts. The material produced by MMEG gives a p⁺ epitaxial silicon layer doped with Al at approximately 2×10¹⁸ atoms-cm^-3. Experimental devices achieve an improvement of 30-40 mV in open circuit voltage over the standard BCSC indicating a significant improvement in rear surface passivation