太陽能電池不銹鋼基板光捕捉改善研究

The light trapping improvement research of stainless steel made substrate solar cell

林志遠(Chih-Yuan Lin)

指導教授 ： 李碩仁

元智大學/工程學院/機械工程學系/碩士(2009年)

https://doi.org/10.6838/YZU.2009.00096

摘要

當太陽能電池薄型化之後，光線行經電池的距離減少，導致電池效率下降，為了增加光線在電池裡的行徑距離，成為研究的方向。
本研究利用不銹鋼為基材，在表面以不同的方式進行加工，產生不同的微結構，改變光線的行徑方向，並以光譜的全/漫反射率為指標。另一方面，利用物理氣相沉積法沉積薄膜，探討薄膜的附著力與電阻率。採用的加工方式有電化學加工、微噴砂與黃光微影製程三種方法，直接在不銹鋼基板上加工出不規則與規則性微結構。不規則微結構是探討不同加工參數下，產生不同的粗糙度，量測粗糙度與光譜之間的關係；規則性微結構是探討不同的光柵幾何形狀與尺寸大小，對光譜的影響。
從光譜量測結果可知，在不規則微結構部份，當電化學的加工電流密度與加工時間增加時，表面粗糙度與漫反射率隨之增加；全反射率部份則無明顯差異。另一方面，微噴砂加工所提升的漫反射率高於電化學加工，約高10%~20%。
在規則性微結構部份，ㄇ字形光柵週期減小與光柵高度增高，其漫反射率隨之增加，全反射率則維持在80%以上；U字形光柵的漫反射率高於ㄇ字形光柵，且鍍銀後的U字形光柵，全/漫反射率皆在80%以上，與無微結構的漫反射率相比較，提升70%~80%。
在附著力測試部份，是以ASTM-D3359的規範進行測試，利用鈦薄膜當不銹鋼基板與銀薄膜的黏著層，能有效提高附著力，測試結果由0B提升至5B；在有微結構基材的測試下，其結果仍為5B。氧化鋅薄膜部份，沉積薄膜時利用高溫製程，提供良好的附著力，其附著力測試結果為5B。
在電阻率的部份，銀薄膜的電阻率遠小於氧化鋅薄膜的電阻率。若預降低氧化鋅薄膜的電阻率，改用氧化鋅摻雜鋁的靶材或降低沉積氧化鋅薄膜製程中的氧氣流量，以提高電性。

關鍵字

薄膜太陽能電池 ； 光捕捉 ； 織質結構 ； 全反射率 ； 漫反射率 ； 粗糙度

並列摘要

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.

並列關鍵字

Thin film solar cell ； Light trapping ； Texture ； Total reflectance ； Roughness

參考文獻

[29] 俞錫鑫，造船廠室內噴砂場空氣中有機化合物探討，高雄醫學大學醫藥暨應用化學研究所碩士論文，中華民國九十六年一月。

[3] 林柏均，從資源依賴觀點看台灣薄膜太陽能電池產業發展前景，國立清華大學工業工程與工業管理學系碩士論文，2006年

[5] 矽薄膜太陽能電池及生産設備技術研討暨成果發表會講義，經濟技術處、中山科學研究院第二研究所，中華民國九十五年十一月三十日

[9] 李宗欣，基板覆多晶矽薄膜之特性研究，國立成功大學航空太空工程學系碩士論文，2006年

[10] K.Yamamoto, M.Yoshimi, Y.Tawada, Y.Okamoto, A. Nakajima, “Thin film Si solar cell fabricated at low temperature”, Journal of Non-Crystalline Solids 266-269(part 2), pp.1082-1087, 2000.