臺灣博碩士論文加值系統

本研究利用分子束磊晶(MBE)技術於n型砷化鎵(GaAs)基板成長InGaAs耦合量子點作為主動層，製作成高效率中間能帶太陽電池。元件主動層結構分別為九層耦合量子點至三十層耦合量子點、九層耦合量子點綴於井及二接面(Two-junction)太陽電池，並調變每層量子點層之間隔層之厚度(5nm~40nm)及量子點成長溫度(Ts=520oC~540oC)，以探討磊晶中間能帶太陽電池之最佳參數。

研究發現：主動層結構為「十二層耦合量子點且間隔層為15奈米」之樣品(元件編號C529)具有最高轉換效率η=8.9%。透過EQE量測可以觀察到：相較於無量子點結構之GaAs-baseline 樣品(C610)，具量子點結構的樣品可吸收波長900nm-1100nm的多出光子，提高元件短路電流，證明我們成功地實現中間能帶的結構。而「十二層耦合量子點且間隔層為15奈米」之樣品其轉換效率η=8.9%已超越GaAs-baseline樣品η=7.5%，證實了耦合量子點之結構能實現中間能帶太陽能電池。而二接面太陽電池(元件編號C493)由I-V曲線判斷可以視為兩個太陽電池正反相接的結果。

接著利用原子層沉積技術(ALD)將樣品鍍上50nm-Al2O3(n=1.6) /50nm-HfO2 (n=2.3)複合鈍化層並作為抗反射層，減少元件表面反射率，提升元件短路電流，使得樣品C529轉換效率由8.9%增加至12.3%，提升了原本效率的1.38倍。

最後，將樣品進行高聚光I-V量測，太陽數範圍從10個到100個，由於開路電壓與太陽數之對數成正比，最後可以探討出轉換效率在多倍太陽數下可以有所提升，皆可提升2.5%~3.2%之轉換效率。

Molecular beam epitaxy (MBE) is utilized for growing InGaAs coupled quantum dots on n-type GaAs substrates as the active layer to produce high-efficiency intermediate band solar cells. The structure of the component active layer is 9-layer to 30-layer coupled quantum dots (coupled QDs) and 9-layer coupled quantum dots in wells (coupled DWells) and two-junction solar cells. The spacer thickness (5nm~40nm) of each quantum dot layer and the quantum dot growing temperature (Ts=520oC~540oC) are controlled to discuss the optimal parameters for epitaxy intermediate band solar cells.

Research findings show that the sample (component No. C529) with the active layer structured “12-layer coupled quantum dots with the spacer 15nm” presents the highest conversion efficiency η=8.9%. It is observed that the samples which possess the quantum dot structure could absorb additional photons with the wavelength 900nm-1100nm by EQE measurement (comparing to the samples which was without quantum dot structure, component No. C610), so that the short-circuit current of the component will be enhanced. It proves the successful implementation of the intermediate band structure in this study. The conversion efficiency η=8.9% of the sample with the active layer structured “12-layer coupled quantum dots with the spacer 15nm” exceeds the GaAs-baseline sample η=7.5%, proving that the coupled quantum dot structure could implement intermediate band solar cells. On the other hands, the two-junction solar cell (component No. C493) could be regarded as the connection of positive and negative between two solar cells from the I-V curve.

Atomic layer deposition (ALD) is further utilized for coating 50nm-Al2O3 (n=1.6) /50nm-HfO2 (n=2.3) composite passivation layer on the sample as the anti-reflection layer to reduce the component surface reflectance and enhance the component short-circuit current. The conversion efficiency of the sample C529 therefore increases from 8.9% to 12.3%, about 1.38 times of the original efficiency (without coating any oxide layer).

Finally, the sample is proceeded the high-concentration I-V measurement (sun numbers are from 10suns to 100suns). Since the open-circuit voltage is proportional to the logarithm of solar cell number, the conversion efficiency would be enhanced about 2.5%~3.2% under multiple numbers of solar cells.

致謝 ii
摘要 iii
Abstract iv
目錄 vi
圖目錄 viii
表目錄 xii
第一章 緒論 1
1.1前言 1
1.2研究動機 2
1.3中間能帶(intermediate band, IB)介紹與基本原則 4
1.4研究方法 7
第二章 理論基礎與文獻回顧 8
2.1太陽電池原理 8
2.1.1 太陽光光譜 8
2.1.2太陽電池基本工作原理 10
2.1.3太陽電池的電路模型 11
2.1.4 太陽電池重要參數 12
第三章 研究方法與儀器架構 15
3.1實驗樣品介紹-耦合量子點太陽電池結構 15
3.2太陽電池製程步驟(黃光製程) 24
3.2.1電極圖形製作 24
3.2.2表面濕蝕刻條件測試 26
3.2.3利用原子層沉積技術(ALD)沉積鈍化層(抗反射層) 27
3.2.4定義元件主體 29
3.3光激螢光量測(PL) 31
3.4外部量子效率量測(EQE) 33
第四章 實驗結果與分析 34
4.1主動層結構差異性之分析 34
4.1.1光激螢光光譜分析(PL) 34
4.1.2不同電極圖形分析 40
4.1.3元件I-V量測與外部量子效率(EQE)量測分析 42
4.2表面鈍化(Surface passivation)改善太陽電池效益 59
4.2.1 不同結構主動層表面成長複合鈍化層優化轉換效率 60
4.3高聚光太陽能 65
4.3.1高聚光太陽能公式 65
4.3.2高聚光太陽能分析 66
第五章 結論 75
參考文獻 77

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