标题: | 新颖矽量子点薄膜应用于太阳能电池之开发 Development of novel Si quantum dot thin films for solar cells application |
作者: | 郭光扬 Kuo, Kuang-Yang 李柏璁 Lee, Po-Tsung 光电工程研究所 |
关键字: | 矽量子点;氧化锌;渐变矽过多氧化矽;太阳能电池;Si quantum dot;ZnO;gradient Si-rich oxide;solar cell |
公开日期: | 2013 |
摘要: | ‘温室效应’与‘能源危机’乃攸关未来人类生存的两大重要议题,永续再生能源加速发展已刻不容缓,而太阳能电池(Solar Cell, SC)一直被视为极具潜力的再生能源之一。于考量电池效率、成本和寿命等关键因素下,矽基SC仍是最具有优势可达到普及化的电池种类;为了达到高效率低成本(第三代SC)矽基SC,开发具有多重能隙的多接面元件结构以有效减低光损耗是不可或缺的要件。 有鉴于矽量子点的独特光学特性,我们提出并开发‘渐变矽过多氧化矽多层膜’与‘氧化锌矩阵材料整合’,期望能在保有矽量子点特性下,同时克服目前应用于SC所遭遇的载子传输效益明显受限的瓶颈,以制作出更具应用潜力的新颖矽量子点薄膜。此篇论文首先即介绍SC的重要性和发展现况,与目前矽量子点应用于SC的优势与挑战,并提出我们的研究目的且简介此研究过程中的相关制程与分析仪器。 为制作出超高密度矽量子点薄膜,我们舍弃传统的[二氧化矽/矽过多氧化矽]多层膜结构,改以‘渐变矽过多氧化矽多层膜’做为新沉积结构;实验结果显示,藉由周期性矽氧原子浓度差异分布,可使矽过多原子于退火过程中自组织形成超高密度且均匀尺寸的奈米结晶矽量子点,此外,该新结构亦大幅提升矽量子点薄膜的光吸收系数与电传输效益,证明利用此新结构,可有效缩短矽量子点间距,以大幅提升矽量子点薄膜的光伏特性。 为形成更佳的载子传输机制,我们亦开发‘氧化锌矩阵材料整合’,因氧化锌薄膜除具备直接宽能隙半导体特性之外,更罕见地同时拥有高透明度和高可调电性等优势,故相当适合做为矽量子点矩阵材料并应用于SC;实验结果指出,针对该矽量子点埋入式氧化锌薄膜,除在长与短波长波段皆可分别保有氧化锌的高光穿透与高光吸收特性之外,中波长波段亦具有来自矽量子点的光吸收与光激发光特性,证实来自矽量子点贡献的光学次能隙形成;此外,相较于使用传统矽相关介电矩阵材料,该矽量子点薄膜具有更高的导电度,且其载子主要经由氧化锌矩阵传输而非传统的量子点间穿隧效应传输,此经矩阵传输机制将可大幅提升矽量子点薄膜的载子传输效益,未来亦可更提升矽量子点应用于SC的优势。 因此,此篇论文中,藉由分别开发新沉积结构与新矩阵材料,我们成功制作出更具潜力且更适合整合于矽基SC的新颖矽量子点薄膜,而根据此研究成果,我们更深信未来若能成功整合此新颖矽量子点薄膜,将可有利于矽基SC的发展,并加速迈向第三代SC的目标。 In order to resolve the critical issues of “Green House Effect” and “Energy Crisis” for humanity’s future, the accelerated developments of renewable energies are necessary. Among all of the renewable energies, solar cells (SCs) are highly considered as the most potential one. To ponder these key factors of efficiency, cost, and lifetime, undoubtedly, the Si-based SCs have the most advantages on popularized developments in the future. However, to successfully achieve high efficiency and low cost, also called the third generation SC, the tandem Si-based SCs with multi-bandgap is required to efficiently reduce the mismatched photon energy loss. Based on the unique properties of Si quantum dot (QD), we propose to develop the novel Si QD thin films by utilizing a gradient Si-rich oxide multilayer (GSRO-ML) structure and integrating with ZnO matrix material to overcome the bottlenecks of the largely limited carrier transport efficiency in the Si-based SCs integrating Si QDs. In the beginning of this dissertation, we talk about the importance and recent developments of SCs, and then, the advantages and challenges of SCs integrating Si QDs are discussed. After that, our motivations, fabrication process, and apparatus are also introduced in details. To achieve the formation of super-high density Si QD thin films, we forsake the traditional [SiO2/SRO]-ML structure and develop a new one, GSRO-ML. In our results, by utilizing the periodical variations in Si/O atomic concentration during deposition, the Si QDs with super-high density and good size control can be self-assembled from the uniform aggregations of Si-rich atoms during annealing. Besides, the considerable enhancements on photovoltaic properties are also obtained by using a GSRO-ML structure due to the improved carrier transport efficiency and larger optical absorption coefficient. To obtain the better carrier transport path for the Si QD thin films, we also develop a new matrix material, ZnO, because it has many desirable features, such as wide and direct bandgap, high transparency, and highly tunable electrical properties. In our results, though embedded with Si QDs, the optical properties of ZnO thin film can be preserved in the long- and short-wavelength ranges. In the middle-wavelength range, the significantly enhanced light absorption and the unusual PL emission peak, owing to embedding Si QDs, are observed. These results represent the sub-bandgap formation in ZnO thin film by utilizing Si QDs while maintaining the essential optical properties of ZnO matrix. In the electrical properties, the Si QD embedded ZnO thin film reveals the significantly higher conductivity than that using SiO2 matrix material. Besides, the carriers transport mainly via ZnO matrix, not through Si QDs, is clearly observed. This unique transport mechanism differing from those using the traditional Si-based dielectric matrix materials has great potential on leading to the much better carrier transport efficiency and electrical properties for SC applications. In this dissertation, we had demonstrated the proposed novel Si QD thin films, utilizing a GSRO-ML structure and integrating with ZnO matrix material, are more suitable and advantageous for the Si-based SCs integrating Si QDs. Therefore, the high-efficiency Si-based SCs integrating Si QDs can be most definitely expected using the novel Si QD thin films. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT079724813 http://hdl.handle.net/11536/73287 |
显示于类别: | Thesis |
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