缺陷調變和導納頻譜分析於銅鋅錫硫硒太陽能電池之研究

在過去幾十年中，從單結晶矽系薄膜技術，許多有潛力的太陽能電池的概念已經開發，並得到越來越多的學術界和業界人員的深入研究。在薄膜太陽能電池技術之中，和銅銦鎵硒光伏類似的kesterite晶相-銅鋅錫硫太陽光伏，因為其地球豐度和低成本之要求等優點，令其成為一個極具潛力的下一代薄膜太陽能電池材料。與CIGS太陽能電池相比，地球上豐富的鋅和稀有昂貴的錫取代銦和鎵。儘管目前溶液法製成的已超過12％的功率轉換效率, 與銅銦鎵硒和碲化鎘太陽能電池相比CZTS作為光吸收材料的銅鋅錫硫太陽能光電發展, 仍然落後於研究學者對於此材料之深度基礎理解，以及精準控制位在銅鋅錫硫吸收層與鉬金屬基板之間的二硫化鉬層厚度。因此，本論文針對此領域的三個關鍵領域做更進一步之研究改善：（1）缺陷特徵及其與光載子動力學的關係; （2）優化改善銅鋅錫硫-鉬金屬(CZTS / Mo)接面，以減少二氧化鉬層之形成，期望更進一步改善元件性能表現和（3）以無毒環保之溶劑製備溶液以發展更大規模的生產。首先，我們探索了各種前驅物系統，例如無毒性的有機溶劑混合奈米金屬顆粒，此已成功地發展成良性溶劑體系中的CZTS分子溶液。均相前驅物為主之溶液也成功開發並證明可提供更精確的單一晶向和元素組成控制。此外，吾人亦開發以真空濺射系統為主之高效率太陽能電池。在這項工作中，我們進一步研究了一種有效的緩衝層來改善光載子傳輸行為。另外，一個有發展性的技術 - 鈉摻雜的雙向表面處理- 已經在CZTS太陽能電池證明可用來調控缺陷特性和其太陽能光電元件表現。最後，通過使用光學和電性鑑定，我們仔細地研究材料本身和不同材料接面處的缺陷特性，及其對於光載子複合行為之連帶影響。上述結果證明鹼金屬於銅鋅錫硫本身和銅鋅錫硫-鉬金屬接面上的缺陷濃度和太陽能電池中光載子傳輸行為影響的重要性。

關鍵字

銅鋅錫硫；太陽電池；缺陷調變；載子動態學；導納頻譜；阻抗頻譜

並列摘要

In the past decades, numerous promising solar cell concepts, ranging from single-crystallized silicon to thin-film based technologies, have been developed and are being studied intensely by an increasing number of scientific groups and companies. Within the thin-film based photovoltaic technology, kesterite-based Cu2ZnSn(S,Se)4 (CZTS) photovoltaics, which is the analogous of Cu(In,Ga)(S,Se)2 (CIGS) photovoltaics, has emerged as a potential candidate absorber material for the next generation thin film solar cells due to their advantages of earth-abundance and low-cost requirements. Compared with CIGS photovoltaics, the earth abundant zinc and the rare and expensive tin replaces indium and gallium in the CZTS absorber. In spite of the latest demonstration of solution-processed CZTS devices over 12% power conversion efficiency, the development of CZTS as an absorber material is still behind in terms of both fundamental understanding of the material system and in the capability to precisely control the formation of MoSe2 layer underneath of the absorber CZTS and Mo substrate for high-efficiency CZTS device, as compared with those of CIGS and CdTe. Therefore, this dissertation targets three key areas in this field: (1) Defect characterization and its relationship to carrier dynamics; (2) Modification of the interface of CZTS/Mo to reduce the formation of MoSe2 in order to improve the device performance and (3) Solution-processing with environmentally friendly solvents for large-scale production. For starters, we explored various precursor systems, such as benign organic solvents, nano-metallic particles, and have successfully processed CZTS from a molecular solution in a benign solvent system. A homogeneous precursor solution has also been developed and proved to offer more precise phase and composition control. Moreover, the high-efficiency CZTS solar cell has also been developed by vacuum-based sputter system. In this work we further investigated an effective buffer layer to improve the carrier transport behaviors. Furthermore, a promising technique – Bifacial sodium-incorporated treatment – has been applied in the CZTS solar cells to manipulate the defect properties and the relating device performance. Lastly, by using electrical and optical characterization, we have conducted detailed investigations on the bulk and the interface defects that govern the carrier recombination and the resulting device characteristics. Aforementioned results reveal the effects of the alkali metals in CZTS and the importance of interface of CZTS/Mo on the defect concentration and on carrier dynamics of the solar cells.

並列關鍵字

Cu2ZnSnS4 ； Solar cell ； Defect engineering ； Carrier dynamics ； Admittance spectroscopy ； Impedance spectroscopy

參考文獻

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缺陷調變和導納頻譜分析於銅鋅錫硫硒太陽能電池之研究

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