In this work, we develop a fabrication process for an interdigitated back contact solar cell using BBr 3 diffusion to form the p + region and POCl 3 diffusion to form the n + regions. We use the industry standard technology computer-aided design modelling package, Synopsys Sentaurus, to optimize the geometry of the device using doping profiles derived from electrochemical capacitance voltage measurements. Cells are fabricated using n-type float-zone silicon substrates with an emitter fraction of 60%, with localized back surface field and contact holes. Key factors affecting cell performance are identified including the impact of e-beam evaporation, dry etch damage, and bulk defects in the float zone silicon substrate. It is shown that a preoxidation treatment of the wafer can lead to a 2 ms improvement in bulk minority carrier lifetime at the cell level, resulting in a 4% absolute efficiency boost. exceptionally high lifetimes can be achieved owing to the high purity of the material. 5 However, recent work by Grant et al has demonstrated that FZ silicon contains defects, which are incorporated during crystal growth. 6,7 In as-grown samples, the defects are essentially latent, but they become activated as recombination centres upon heat-treating FZ silicon at temperatures between 450°C and 750°C.Thus, although the as-received lifetime is very high, the lifetime can
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