利用濕式蝕刻法對太陽能電池織質化表面與黑色奈米級織質化表面之比較

Abstract

本論文乃利用濕式蝕刻法對矽基板之織質化表面（texture surface）與黑色奈米級織質化表面(black nanoscale texture surface)應用在矽基板太陽能電池上作一比較；首先，利用市面上常用濕式化學蝕刻法(不同蝕刻溶液)在單晶矽與多晶矽基板上形成織質化結構，量測其反射率的變化；另一方面，在單晶矽與多晶矽表面沉積一層金薄膜，利用快速退火製程在矽基板上形成保護罩(mask)，接著利用濕式化學蝕刻在矽基板上形成奈米級黑色織質化表面，此方法可適用在單晶矽與多晶矽基板上。實驗結果顯示織質化表面（texture surface）與黑色奈米級織質化表面(black nanoscale texture surface)皆可有效降低矽晶片的反射率。 並利用實驗所量測得到的反射係數（reflectance）以PC1D模擬軟體做電池效率之模擬，模擬結果顯示黑色奈米級織質化表面應用在太陽電池上可以改善織質化表面太陽電池效率約0.74%。 另外，將織質化表面（texture surface）與黑色奈米級織質化表面(black nanoscale texture surface)應用在矽基板太陽能電池上，利用同一製程條件製作出不同織質化表面太陽電池，並比較太陽電池的短路電流密度(short circuit current density)、填充係數(fill factor)、轉換效率(efficiency)。期望能減少光線的反射，增加光線吸收，提升太陽電池效率。 由實驗結果得到黑色奈米級織質化表面(black nanoscale texture surface)應用在矽基板太陽能電池上最大可以改善織質化表面（texture surface）太陽電池0.6%。

This thesis focuses on the study of the texture of the Si surface for anti-reflection purpose. The anti-reflection property studied in this thesis the black color nanometer scale texture on Si surface. The efficiency and characteristics of the conventional surface texture and black non-reflect structure applied of solar cells are compared. The single silicon ( <100> orientation, single side polished) was etched using alkaline etchants (KOH、NaOH), pyramidal texture was formed on the Si surface after etch. The reflectance was reduced from 70% to below 5% after the texture formation on the surface. The isotropic etchant was also used to etch the poly silicon. After isotropic etcheing, a rounded surface texture formed. It was below 0.2% and lower then the as-cut poly Si. The subwavelength silicon structure was etched in an aqueous solution. After etching, the nanoscale texture of silicon surface formed. The treated area of all samples appeared in black color. This treatment can be applied to different types of Si substrates including single and poly crystals. The single-crystalline silicon reflectance decrease from 35~70% down to 0.01~10 % especially at short wavelength. For poly Si after black nonreflecting treatment, the reflectance decreased from 0.14 % down to below 0.03 %. In this research, simulation was performed using PC1D version 5.9. For Si solar cell with black surface treatment, the efficiency was improved by 0.74% as compared cells with conventional texture surface. Si solar cells with different types of surface texture was evaluated and I-V curve was measured. For single crystal Si solar cell with black surface treatment (SWS solar cell), the efficiency was improved by 0.6% (etched 45sec SWS) and 0.31% (etched 135sec SWS) as compared with pyramidal texture surface solar cell which was etched using conventional etching solutions.