| Summary: | 碩士 === 元智大學 === 機械工程學系 === 97 === As solar cell becomes thinner in thickness, it reduces the light traveling distance within the cell and therefore results a decline in efficiency. This research is established in order to increase the light traveling distance in the cell.
In this research, stainless steel is used for the substrate; the surface is processed by different methods to create different texture in order to alter the direction of the light. The total/diffuse reflectance within the spectrum are set to be the benchmark values. At the same time, Physical vapor deposition (PVD) is utilized to deposit films, and further to discuss their adhesion and resistivity. The processing methods include Electrochemical Machining (ECM), sand blasting, and NEMS technology to directly process on the stainless steel surfaces. Within this study, irregular texture and regular texture are discussed. Experiments and researches were conducted to demonstrate the causal effects between the resulted roughness and different process variables, further discussion is also provided to show the relationship between the roughness and spectrum; as for the regular texture section, we are interested in how different grating geometry shapes and sizes would impact the spectrum.
From the spectrum test result, it indicates that the surface roughness and diffuse reflectance will increase along with the current density and process time for irregular texture; however, the total reflectance shows no significant differences. On the other hand, the sand blasting process is able to provide higher diffuse reflectance than ECM by 10%~20%.For the regular texture, the diffuse reflectance in rectangle grating is positive proportional to the grating height and negative proportional to the grating period; the total reflection is maintained above 80%. The diffused reflectance of U-shape grating is higher than the rectangle grating, besides, the total/diffuse reflectance are both above 80% for the silver coated U-shape gratings. This result shows a 70%~80% enhancement compare to the plate in diffuse reflectance.
Speaking about the adhesion test, ASTM-D3359 standards were followed to complete this assessment. Ti film is used for the adhesive section between the stainless steel and the silver film which is able to strengthen the adhesion from 0B to 5B according to the ASTM-D3359. Regard to the zinc oxide (ZnO) film adhesion test, it shows that by performing the process under high temperature will help to achieve better adhesive ability with a result of 5B in the test.
As for the resistivity, silver film is far less than ZnO film in resistivity. If resistivity is not desired, changing the ZnO target to Aluminum-doped zinc oxide (AZO) target or reducing the oxygen flow while coating ZnO film will help to increase conductivity.
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