- 學位論文
製作抗反射膜及表面粗糙化以作為太陽能電池之應用
Fabrication of Antireflection Coatings and Surface Texture for Solar Cell Application
摘要
在表面未做任何改善處理的太陽電池，由於折射率與入射介質之折射率不同，而導致入射光在電池表面的光學反射損失相當的大，所以必須針對表面作改善才能有效地降低光在表面的反射損失，進而提升入射光至電池內部的機會，能夠將光有效地完全利用，進而提升太陽能電池的轉換效率。 因此本研究主要是針對表面作改善處理（抗反射薄膜及表面粗糙化），期望可在所選定的頻譜範圍內獲得反射率的降低。在抗反射膜的部份，先將所選定的單層抗反射層材料SiO2、TiO2和Si3N4利用光學模擬軟體作為輔助，分析其光學特性，得出在光學厚度等於λ/4時，會有最低反射率，接著實際以射頻磁控濺鍍(rf magnetron sputtering)法製作出單層抗反射層，可得知平均反射率分別為12.50 %、9.62 %和5.52 %，可將表面未做處理之矽晶裸片的平均反射率降低66.79 %、74.44 %和85.33 %；在雙層抗反射膜的部分，將所選定的三種抗反射層材料，以常見的光學厚度λ/4-λ/4兩兩堆疊，在SiO2/Si3N4/Si堆疊部分，得出平均反射率為8.39 %，可將矽晶裸片的反射率降低77.70 %。而在SiO2/TiO2/Si光學厚度堆疊部分，可得出平均反射率為4.09 %，將矽晶裸片的反射率降低89.13 %。另一方面則針對基準太陽光最強放射照度所位於波長550 nm優化得出厚度做堆疊，發現在SiO2/Si3N4/Si堆疊部分，結果比所選出常用光學波長的堆疊，產生降低頻譜範圍內平均反射率的效果還要好。而在SiO2/TiO2/Si光學厚度堆疊部分，與所選出常用光學波長的堆疊相比得知，在頻譜範圍內降低平均反射率的效果類似，但可以用較薄的厚度堆疊。 在另一項表面作粗糙化改善的部分，將矽晶裸片放入已調配好之氫氧化鈉（NaOH）、異丙醇（IPA）及去離子水（DI water）混合蝕刻液中，以形成錐狀結構（random pyramid structure），使光入射至粗糙表面時，能夠增加光的入射機率，可將原本表面未經過任何處理之矽晶裸片之平均反射率降低70 %，進而有效提昇太陽電池的效率。 最後將抗反射膜及表面粗糙化應用於太陽能電池上，結果藉著降低入射光在表面的反射，增加入射至電池內部的機會，進而提昇太陽電池之效率。
並列摘要
If the surface of solar cell device without antireflection coating(ARC) or texture on the surface, will exhibit great reflective losses of incident light because the refractive index is different from that of the incidence medium. Reducing the reflectance of incident light can increase the chance of the light transmitting into the device, and then increase the efficiency of the solar cell. The surface of the solar cell must be improved. In this research, ARC and surface texture are attempted to use to reduce the reflective loss of the solar cell over the spectral range we selected. In the part of AR layers, the single layer ARCs, such as SiO2, TiO2 and Si3N4, were studied. The software was used to simulate and analyze their optical characteristic. From the analysis result of software, the optical thickness of λ/4, will give a minimum reflectance. Single layer ARCs deposited by rf magnetron sputtering will give the average reflectance of 12.50 %, 9.62 % and 5.52 % for SiO2, TiO2 and Si3N4, respectively. They can reduce the average reflectance to 66.79 %, 74.44 % and 85.33 %, respectively, as compared to bare silicon without any treatment. In the part of the double AR layers, we designed optical thicknessλ/4-λ/4 of two common stack. For SiO2/Si3N4/Si stack, the reflectance is 8.39 %, and reduces the average reflectance about 77.70 % of bare silicon. For SiO2/TiO2/Si stack, the reflectance is 4.09 %, and reduces the average reflectance about 89.13 %. On the other hand, we optimize the thickness for wavelength lain in 550nm of the strongest sunlight energy. For SiO2/Si3N4/Si stack, its effect is better than the common stack of optical thickness over the spectral range we selected. For SiO2/TiO2/Si stack, its effect is similar to the common stack of optical thickness, but we can deposit them with thinner thickness. For another part of surface texture treatment, we put bare silicon into the etching solution composed with NaOH, IPA, and DI water in order to form random pyramid structure on the surface. The structure can increase the probability of incidence light, reduce the average reflectance about 70 %, and increase the efficiency of the solar cell effectively, Finally, we apply ARCs and texture structure on the solar cell surface, in order to reduce the reflectance of incident light on the surface, increase the chance of the light transmitting into the cell, and then improve the efficiency of the solar cell.