Corresponding relation between PL of multicrystalline silicon wafers and solar cell efficiency

Various market factors (e.g., anti-dumping and anti-bribery, subsidy retreat, etc.) have accelerated technology upgrading and cost efficiency of PV industry. Improving conversion efficiency is an effective way to reduce cost. Mainstream silicon wafer manufacturers are intensifying research and development of "the next generation high-efficiency multicrystalline silicon wafer" that is of higher efficiency. It is essential to obtain the cell efficiency parameters at silicon wafer-side. This work analyzes the relationship between PL image parameters of multicrystalline silicon wafer measured by photoluminescence tester (PL) and the corresponding cell conversion efficiency, and the relationship between parameters of PL image and cells. Firstly, an analysis software is independently compiled to analyze the "black silk" and "normalized intensity" parameters of PL image, with the numerical results of the corresponding silicon wafers calculated. Selected high efficiency multicrystalline silicon bricks are cut into silicon wafers of 190 mu m thickness, which are put to tests sequentially on the PL images of multicrystalline silicon wafers and then made into solar cells. The producing process of solar cells includes ordinary acid texturing, diffusion, removal of phosphosilicon silicon glass (PSG), plasma chemical vapor deposition (PECVD), screen printing, etc. Then cell efficiency and V-oc parameters thereof are tested, with the correspondence between cell efficiency and parameters thereof and the PL parameters. The experimental data show that the tail is mainly affected by large grain boundaries and high impurity content. The correlation deviation of the cell efficiency, "normalized strength" of V-oc and PL images, and "black silk" ratio parameters are greater than those of the middle section and the head. The "black silk" ratio is low, and its solar cells efficiency and V-oc are high. The "normalized strength" of PL images is high, and its solar cells efficiency and V-oc are high. But the "normalized strength" of PL images and V-oc of cell have strong correlation with "black silk" ratio of PL images, and the "normalized strength" and "black silk" ratio of PL images have weak correlation with cell conversion efficiency. The reason is that material properties of PL photoluminescence test silicon wafer are related to the corresponding cell V-oc, and cell conversion efficiency is affected by many factors: texture, diffusion, coating processes, etc. In this paper, the expression of "normalized strength" of PL and cell V-oc is deduced based on the semiconductor correlation principle. It is proved that the "normalized strength" of PL is strongly correlated with that of cell V-oc in principle. The "normalized strength" of PL obtained by the analysis has the closest correlation with the quality of multicrystalline silicon wafers, which can be better used to guide the quality improvement of multicrystalline silicon wafers.