TAILIEUCHUNG - Solar Cells Silicon Wafer Based Technologies Part 6

Tham khảo tài liệu 'solar cells silicon wafer based technologies part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 116 Solar Cells - Silicon Wafer-Based Technologies As mentioned above all samples contain a swirl defect. If you look at the pictures produced by red LED wavelength 650 nm figs 6 and 7 this defect is clearly visible. Fig. 8. Analyses of output local current of the sample no. 1 by usage of focused LED diode with middle wavelength 560 nm green LED T 297 K Fig. 9. Analyses of output local current of the sample no. 1 by usage of focused LED diode with middle wavelength 560 nm green LED T 297 K Possibilities of Usage LBIC Method for Characterisation of Solar Cells 117 For the green LED diode middle wavelength 560 nm figures 8 and 9 the defect is still well visible but not as well-marked as for the red colour middle wavelength 650 nm . From the principle of photovoltaic effect it is clear that the light with sufficiently long wavelength passes through the solar cell without generation of photocurrent. With a shorter wavelength the light is absorbed faster from impact light to solar cell and that is why the penetration depth is shorter. The wavelength of red light is the longest for the used light sources therefore the penetration depth is the longest. This is proven by well-market visibility of swirl defect which is the defect made in bulk of material. Along the way the wavelength of blue light is the shortest and it causes the full loss of visibility of this defect. This is caused by the absorption of the light near the solar cell surface where the swirl defect is not taking effect yet. The wavelength of green color light is between the wavelengths of red and blue color light. Therefore the green color light penetrates to a deeper depth than the blue color light but not so deep as the red color light. The swirl defect for the blue color wavelength 430 nm figures. 10 and 11 is almost invisible. We may think that the blue color light is not important for LBIC diagnostic because it does not allow the bulk defect detection. If you look at the figure closely you can observe

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