PL photoluminescence imaging solar cell production inspection equipment

In recent years, the photovoltaic industry has developed rapidly, and improving efficiency and reducing costs have become the goals of the entire industry. In the process of thinning crystalline Si solar cells, many serious problems have emerged, such as fragments, hidden cracks in the cells, surface contamination, poor electrodes, etc. It is these defects that limit the photoelectric conversion efficiency and service life of the cells. At the same time, due to the lack of perfect industry standards, the quality of Si wafer raw materials is also uneven, and the existence of some defective wafers directly affects the stability of the components and even the photovoltaic system. Therefore, the solar industry needs a fast, effective and accurate positioning inspection method to detect problems that may occur in the production process.
The luminescent imaging method provides a very good solution for solar cell defect detection. This detection technology is easy to use and is similar to perspective two-dimensional surface detection.

Photoluminescence (photoluminescence , PL) The detection process generally includes laser absorption by the sample, energy transfer, light emission and CCD There are four stages of imaging. Laser is usually used as the excitation light source to provide photons of a certain energy. Si The electrons in the ground state of the film enter the excited state after absorbing these photons. The excited electrons are metastable and will return to the ground state in a short time and emit 1150 nm The infrared light is the peak of the fluorescence. The cooled camera lens is used for light sensing, and the image is displayed by the computer. The intensity of the luminescence is proportional to the density of the unbalanced minority carriers at the location, and the defect will become a strong recombination center for the minority carriers. Therefore, the minority carrier density in the area becomes smaller, resulting in a weakened fluorescence effect, which appears as dark points, lines, or certain areas on the image, while the area with less recombination in the cell appears as a brighter area.

Therefore, by observing the photoluminescence imaging, it is possible to determine Si Whether there are defects in the chip or battery cell.

The operation interface is as follows

The test sample example is as follows:

PL test equipment performance parameters