Influence of the Bulk Resistivity on Silicon Heterojunction Solar Cells and Module Reliability

Recent developments in industry on surface passivation open the possibility of using less doped substrates in silicon solar cells. We investigate how the bulk resistivity affects the performance of silicon cells and the reliability of modules. Herein, n- and p-type silicon heterojunction cells with bulk resistivities between 3 and 15 000 52cm are studied. We measure the current-voltage characteristics of n-type cells across the resistivity range, and we find comparable responses to illumination intensities between 0.1 and 1 suns. The cells with bulk resistivities over 1000 Omega cm show breakdown voltages larger than -1000 V, almost two orders of magnitude higher than in typical commercial cells. Although modules have bypass-diodes to prevent cells from going into breakdown, higher breakdown voltages can improve the reliability of modules in case of bypass-diode failure and reduce the module cost by easing the number of bypass-diodes required. Finally, the cells have been submitted to light soaking. The float-zone p-type cells with bulk resistivities over 10 000 Omega cm are less sensitive to light-induced degradation than cells with bulk resistivities below 10 Omega cm. The former show to recover few hours after light soaking, while the latter recover only after dark annealing.

Automated summary

Recent developments in surface passivation technology have enabled the use of less doped substrates in silicon solar cells. In this study, we investigate the impact of bulk resistivity on the performance and reliability of silicon cells. We find that higher resistivities lead to increased breakdown voltages and improved module reliability. Moreover, cells with higher resistivities recover faster after light soaking.