Sulfur-enhanced surface passivation for hole-selective contacts in crystalline silicon solar cells

Effective surface passivation is pivotal for achieving high performance in crystalline silicon (c-Si) solar cells. However, many passivation techniques in solar cells involve high temperatures and cost. Here, we report a low-cost and easy-to-implement sulfurization treatment as a surface passivation strategy. By treating p-type c-Si (p-Si) wafers with (NH4)2S solution, sulfur can be introduced onto the surface and passivate the dangling bonds by forming an Si–S bond. Sulfurization also contributes to a higher negative fixed charge at the p-Si/Al2O3 interface and, thus, better field-effect passivation. Due to the improved passivation, sulfurization effectively enhances hole selectivity, evidenced by the substantially improved open-circuit voltage and efficiency of solar cells. Eventually, by employing sulfurization in hole-selective contacts, remarkable efficiencies of 19.85% and 22.01% are attained for NiOx- and MoOx-based passivating contact c-Si solar cells, respectively. Our work highlights a promising sulfurization strategy to enhance surface passivation and hole selectivity for dopant-free c-Si solar cells. [Display omitted] •(NH4)2S solution treatment as an effective sulfurization strategy•Sulfurization boosts both chemical and field-effect passivation of the Si surface•Sulfurization improves the hole selectivity of crystalline silicon solar cells•An efficiency (22.01%) of MoOx-based crystalline silicon solar cells Effective surface passivation is crucial for improving the performance of crystalline silicon solar cells. Wang et al. develop a sulfurization strategy that reduces the interfacial states and induces a surface electrical field at the same time. The approach significantly enhances the hole selectivity and, thus, the performance of solar cells.