High Throughput Solar Cell Processing by Oxidation of Wafer Stacks
In this work, we investigate two approachesfor high throughput emitter formation and thermal oxidation for passivated emitter and rear cells (PERC). The low temperature stack oxidation (LoTSOx) approach uses wafer stacks in the typical low temperature thermal oxidation process in the PERC manufacturing sequence. With the LoTSOx approach, we reach similar energy conversion efficiencies of = 22.2% in comparison to state-of-the-art PERC processing but with 3.1 times higher throughput. The second approach, using a shortened low pressure POCl3 diffusion and a high temperature stack oxidation (HiTSOx approach) with laser-doped selective emitter, yields a peak conversion efficiency of = 22.0% and low specific contact resistances c ≈ 0.6 mΩcm2. We further investigate different diffusion and oxidation processes for the HiTSOx approach resulting in a wide range of emitter sheet resistances Rsh. We reach low emitter dark saturation current densities of j0e = 12 fA/cm2 at Rsh = 389 Ω/sq while stacking the wafers during the oxidation process.