EFFECTIVE PASSIVATION OF THE LOW RESISTIVITY SILICON SllRFACE BY A RAPID THERMAL OXIDE/PECVD SILICON NITRIDE STACK AND ITS APPLICATION TO PASSIVATED REAR AND BIFACIAL SI SOLAR CELLS

A novel stack passivation scheme, in which plasma silicon nitride (SiN) is stacked on top of a rapid thennal SiO? (RTO) layer, is developed to attain a surface recombination velocity (S) approaching 10 em/s at the L3 O-cm p-typc (l00) silicon surfaee_ Such low S is achieved by the stack cven when the RTO and SiN films "I<ilvldllally yield considerably poorer surface passivation. Critical to achieving low S by the stack is the use of a 'hon. moderale temperature anneal (in this study 730°C for 30 seconds) after film growth and deposition. This ,mneal is believed to enhance the release and delivery of ato'mie hydrogen from the SiN film to the Si-Si02 interface, thcreby reducing the density of interface traps at the surface. Compatibility with this post-deposition anneal makes thc stack passivation scheme attractive for cost-effective solar cell production since a similar anneal is required to lire scn~en-printed contacts. Application of the stack to passivated rear screen-printed solar cells has resulted in V",'s of 641 mV and 633 mV on 0.65 O-cm and 1.3 O-cm FZ Si substrates, respecti,vely. These V", values are roughly 20 mV higher than for cells with untreated, highly recomhinative back surfaces. The stack passivation has Ilso been used to form fully screen-printed hi/acia! solar cclls which exhibit rear-illull111l1ated efficiency as high as 11.6% wilh a single layer AR coating. Kcywords: Passivation I: Rapid Thermal Processing 2: Bifacial 3.