MASTERING THE DEFECTIVITY: PREREQUISITE FOR HIGH EFFICIENCY SILICON HETEROJUNCTION SOLAR CELLS

摘要

The crystalline (c-Si) wafer passivation quality is known to be a key factor in the performance of high efficiency silicon based solar cells, among them silicon heterojunction cells (SHJ). During the cell fabrication process, wafers are manipulated via different handling systems entering in contact with the bare or weakly protected c-Si surface. Here the passivation quality brought by amorphous silicon (a-Si:H) is likely to be locally degraded. The amount of defectivity is revealed by spatially resolved photoluminescence. In this contribution, an image processing software HETLUMTOOL developed internally at CEA is introduced. It allows for the quantification of the defectivity, that can then linked to cell performance. The cell power conversion efficiency loss due to the defectivity amounts roughly 1.5% for cells produced at CEA [2018 data]. HETLUMTOOL features several options useful in a production line as a check of the correct behavior of the wafer transport system, for various cell technologies. Works done at CEA to reduce the defectivity took an important part in the achievement of the 24.63% cell (total area - 244.3 cm~2) certified SHJ cell produced on an industrial set of tools. More recently a power conversion efficiency of 25.00% was reached (212.84cm~2).