- 學位論文
利用乾式蝕刻技術於次波長結構製作全方位抗反射矽太陽電池特性之研究
Fabrication of omni-directional anti-reflection subwavelength structures on silicon solar cell using reactive ion etching
摘要
我們利用軟體模擬及製作二氧化矽(SiO2)奈米柱作為全方位抗反射層，其目標在降低在不同角度入射光的反射率及提升在不同角度入射光的太陽能電池效率。這種全方位抗反射層製程是在太陽能電池最上層的二氧化矽(SiO2)表面鍍上一層薄薄的銀膜，再利用銀退火後的凝聚性形成奈米大小金屬遮罩，用此遮罩以乾蝕刻(RIE)得到SiO2次波長(Sub-wavelehgth)結構。 我們在1/4 λ厚的SiO2與1/4 λ厚的TiO2上長成300 nm高的SiO2的膜，然後以 CF4乾蝕刻形成300 nm高的奈米柱，形成一具全方位抗反射表面結構。波長在400-1000 nm 此次波長結構之反射率從40 %降到3 %。有全方位抗反射層的太陽能電池相對於無全方向抗反射之太陽能電池的光電流密度從21.6 mA/cm2 提升到30.1 mA/cm2，其效率也從9.00 %上升到12.9 %，整體相對提升效率提升了42 %。另外，光入射角度從0度增加到75度時。表面沒有抗反射結構的矽太陽能電池，光電流密度從21.6 mA/cm2下降到 5.7 mA/cm2，效率從9.00 %下降到2.30 %，相對效率下降74.4 %；而有全方向性抗反射層的矽太陽能電池上光電流密度則從30.1 mA/cm2下降到13.0 mA/cm2，效率從12.9 % 下降到5.4 %，相對效率僅只有下降58.3%。成功驗證全方向次波長表面結構具廣角度入射及寬波段低反射之特性及提升太陽能電池轉換效率的特性。
並列摘要
In this paper we simulate the subwavelength by a software and construct of the silica (SiO2) nanorods as a omni-directional anti-reflection layer. We expect it can reduce the reflection and improve the conversion efficiency from different incidence of light. There are three steps of fabrication to obtain this nanostructure. First, we deposit double layers which are TiO2, SiO2 for anti-reflection on silicon solar cell, before we deposit thin silver (Ag) on the top of solar cell. Second, we anneal the silver to gather as the nanoparticles mask. Finally, we use RIE with CF4 to etch the top SiO2 to form the nanorods form on this device. The device has omni-directional anti-reflection which after we use RIE with CF4 to fabricate 300 nm nanorods upon doubles TiO2/SiO2 AR layers. It reduces the reflection to 3% at the wavelength 400 to 1000 nm ranges. The short-circuit current density increases from 21.6 mA/cm2 to 30.1 mA/cm2 and the conversion efficiency increase a factor of 42 % from 9.0 % to 12.9 % were obtained with nomal incident. When we change incident light from 0o to 75o, Solar cells without anti-reflection coating are generated less short-circuit current density which reduce from 21.6 mA/cm2 to 5.7 mA/cm2 and the conversion efficiency decrease a factor of 74.4% from 9.0% to 2.3%. However, compared the solar cell with omni-directional anti-reflection, the short-circuit current density only reduce to 30.1 mA/cm2 from 13.0 mA/cm2 and the conversion efficiency only decrease a factor of 58.3% from 12.9% to 5.4%. The experimental demonstrated successfully the subwavelength structures which can absorb omni-directional incident and have very low reflection with broadband. According this property, it also increases the conversion efficiency of solar cell.