| 摘要註: |
考量高效率太陽能電池，高聚光大電流操作下，若能有效降低元件之串聯電阻，減少電池本體之功率消耗，將有利於減緩元件之「填充因子」(Fill Factor, FF)隨著光強度提高而劣化的程度，進而改善其高聚光操作下之轉換效率。 本論文旨在研究電極樣式及其相應電阻大小與功耗的關係，經多方考量金屬遮蔽率、電極間距、電流匹配、電流收集面積與微影製程限制…等重要因素後，提出三種新樣式優化電極之設計，包括兩種單漸變樣式：一為與電流收集面有關之階梯式線寬電極樣式(Step Width, SW) 、二乃與電流方向有關之線寬漸變樣式 (Taper)，及一種結合上述兩種設計概念之雙漸變樣式(SW & Taper)。本論文透過演繹優化電極之理論功耗，配合數值模擬評估其電流密度分佈，完成可行性評估後，根據計算結果與設計流程完成光罩設計，並將之導入具電極保護及電池元件單元隔離之優化製程，完成多接面太陽電池元件之製作。 實驗結果顯示，相較於1 Sun (AM1.5) 之結果，於116x Suns聚光下，優化電極可明顯減緩元件「填充因子」的劣化程度，對照組(即線寬無漸變之設計：Normal)劣化達8.8% (FF=86.4%→ 78.8%)，最佳設計(SW&Taper)僅劣化2.1% (FF=87.1%→ FF=84.8%)；因而有效提升轉換效率(η)最佳達18.2% (Taper) (η=23.6%→η=27.9%)，但對照組僅提升轉換效率11.8% (η=22.9%→η=25.6%)。實驗結果顯示，電極設計與「填充因子」劣化程度之關係為：Normal > SW > Taper > SW&Taper。此特性與理論解析及數值模擬之結論彼此呼應且相互吻合。 Considering the high-efficiency solar cells operating under high concentration light intensity with high current, if the series resistance of devices can be reduced to lower power loss of solar cells, it will benefit in maintaining solar cells having a higher fill factor (FF) to improve its conversion efficiency for high concentration operation. In this thesis, we aim to study the relationship between electrode resistance and power loss for various novel developing electrode patterns. By trade off device performances from those considerable parameters related to electrode designs, including metal shadow ratio, grid pitch, current matching, current collecting effective area, photolithography limit, etc, we present three different types of novel optimized electrode – including two 1D-evolution patterns: (1) “Step Width, SW” – width evolution proportional to the effective current collecting area. (2) “Taper” – width evolution depending on current flow direction and current accumulation, and one 2D-evolution pattern which combines the design ideas of (1) and (2) together, called (3) “SW & Taper”. In this study, the electrode power consumption has been evaluated by theoretical analytics; meanwhile, the current density distribution has been identified by numerical simulation. According to calculated parameters, a specific photolithography mask corresponding to our electrode design rules has been prepared. Finally, novel electrode patterns embedded multi-junction solar cells have been successfully fabricated by introducing them into an optimized developed fabrication process, including grid protection and unit cell isolation by SiO2. According to the experimental results, the developed novel electrodes can significantly depress the fill-factor’s getting worse speed. To compare devices performances under 116x Suns and 1 Sun (AM1.5) conditions, the deterioration of fill factor from the reference design (w/o width evolution, named “Normal”) can reach to 8.8% (FF=86.4% → 78.8%); however, the best one from “SW&Taper” can keep a higher fill factor and only 2.1% decreased (FF=87.1% → FF=84.8%). It hence contributes to increase conversion efficiency (η). In case of “Taper”, 18.2% efficiency improvement can be reached (η=23.6% → η=27.9%); however, in case of “Normal”, it only increase 11.8% (η=22.9% → η=25.6%). On the other hand, we have demonstrated the deterioration trend of the fill factor is Normal > SW > Taper > SW&Taper. This feature not only matches to our expectation, but also is consistent with theoretical analysis and numerical simulation results. |