Silicon Heterojunction Solar Cells with High Bulk Resistivities Over 1,000 Ω·cm in Relevant Field Conditions of Illumination and Temperature

As we design solar cells with better surface passivation, it is important to revisit the bulk properties. The use of lightly doped wafers provides a promising way to mitigate Auger recombination and increase the breakdown voltage of solar cells, which could lead to new module and system designs. Thus, studying the performance of silicon (Si) solar cells and modules using such wafers in relevant field conditions is of significant interest. In this study, we experimentally investigate the impact of the bulk resistivity (up to >15,000 Ω.cm) on the properties of Si heterojunction solar cells under different illuminations (0.1-1 suns) and temperatures (25–70 °C). We also study the dependency between the breakdown voltage and the bulk resistivity. The results indicate that for very low illuminations intensities down to 0.1 suns, cells with very high bulk resistivities, over 15,000 Ω·cm, have comparable performances to cells with much lower bulk resistivities. The temperature coefficients measured on these cells are also comparable with values previously reported for cells using wafers with standard resistivities. The cells with bulk resistivities over 1,000 Ω.cm show breakdown voltages larger than -1,000 V, almost two orders of magnitude higher than in typical Si solar cells. Our simulations indicate that in the absence of bypass diodes, shaded solar cells with larger breakdown voltages still operate in forward-bias, even under extreme shading conditions, protecting the integrity of the cell and module. Together, these results highlight the large potential of using high-resistivity wafers to manufacture high-efficiency Si solar cells suitable to operate under relevant field conditions, and with the prospect of more robust and cost-effective module designs.