密堆积硅量子点薄膜材料的结构优化，发光和光伏特性及应用研究

High-brightness Si quantum dot light-emitting diodes (Si QD LEDs) are indespensible for the integrated Si photonics. On the other hand, high efficiency Si QD thin film solar cells are highly pursued in the photovoltaic field recently for its excellent serviceability. The basic geometries for both devices are similar, only the power conversion directons are reverse. A common bottleneck problem for both is how to facilitate carrier transport within Si QD thin film. Normal treatments are chemical and field-effect passivations as well as structural modification. However, none of them can solve the bottleneck problem. In this proposal, we conceive to prepare a noval functional material-closely pack Si QD thin film, so as to drastically reduce the barrier widths among the QDs and meanwhile to increase the Si QD density for enhanced light-emission or photoabsorption. Firstly, by using an approach of oxidation and etching, a large amount of Si QDs with high purity are prepared. A series of post-treatments yield Si QD thin films in an embryonic form. Further, via optimizing the preparation procedure, Si QD thin films with much improved close packed structures are obtained. Such a thin film is in fact a noval man-made crystal material. The light emitting and photovoltaic properties as well as other propeties of such Si QD thin films are investigated. Based on the Si QD thin films, high brightness and three primary color Si QD LEDs as well as Si QD thin film solar cells with high efficiency and long-term stability are studied.

高亮度硅量子点发光二极管（LED）是实现硅光电子集成的关键；而高效的硅量子点薄膜太阳电池，鉴于其适用性，也是近年来光伏领域孜孜以求的目标。二者主体结构相似，能量转化方向相反，当前面临的共同瓶颈问题是如何实现电荷（载流子）在量子点间的有效隧穿迁移。目前通用的方法是对硅材料做化学钝化和场效应钝化及结构处理，但这些均无法根本解决电荷有效隧穿问题。为此，本项目通过研制密堆积硅量子点薄膜功能材料，来大幅减小电荷隧穿的势垒宽度，同时增加硅量子点空间密度。将首先利用氧化-腐蚀方法量产高纯度的、分立的硅量子点，再经过系列后处理方法，制备密堆积硅量子点薄膜材料。之后研究该材料的结构优化，以获取结构良好的密堆积硅量子点薄膜。该材料也是一种新型人工晶体。在此基础上，将开展这种硅材料的发光和光伏特性及其它物性研究，以及高亮度、三原色硅量子点LED和稳定、高效的硅量子点薄膜太阳电池的应用研究。

鉴于硅的高丰度特性、现代硅工艺的成熟性及其产业链的高度完整性，发展硅基的功能材料和硅光电子器件，包括新型吸光材料、光伏材料以及新型硅光源、硅光子探测器和硅太阳电池，对于国计民生以及国家安全具有重要意义。本项目首先发展了多种高密度密堆积硅量子点薄膜材料。之后基于此，研究了宽谱的光致发光和电致发光的全硅白光薄膜，研究了高亮度硅薄膜，研究了全硅激光器，研究了高亮度全硅白光LED。另外，还研究多种增强晶硅太阳电池效率的方法。重要成果包括1）研制成功高光增益硅量子点薄膜，其光增益接近常规III-V族激光材料，达到500cm-1，2）研制成功世界上首个全硅激光器，激射波长在770-780nm，3）在此基础上发展了波长大范围（710-820nm）可调的全硅激光器，4）发展了高亮度全硅白光LED，其外量子效率>5%，5）成功研制了当年度效率最高的黑硅太阳电池（2016年，18.97%光电转化效率），其中的样品处理方法已被当前黑硅太阳电池生产所普遍采用。这些成果均受到国内外媒体的广泛关注，其中光伏研究成果已经应用于产业中；高亮度全硅白光LED将致力于通用照明应用，以部分替代当前基于稀有元素的LED；全硅激光器的应用目标是有源硅光子芯片。项目执行期间，发表项目标注SCI论文13篇，投稿2篇，准备投稿1篇，申请专利5项，培养博士生5人，国际会议报告3次，国内会议报告4次。在材料和器件指标方面，完成项目所有目标。经费使用合理、符合规定。