银纳米簇宽带敏化稀土掺杂近红外下转换发光玻璃研究

This project proposal aims to carry out the fundamental investigation on the new mechanisms, materials and fabrication techniques of silver (Ag) nanoclusters broadband sensitized rare-earth (RE)-doped near-infrared downconversion luminescent glasses and related optoelectronic devices for enhancing the efficiencies of crystalline-silicon solar cells. The widely investigated RE3+-Yb3+ (RE = Tb, Pr, Tm, Ho, Er) downconversion couples possess a fundamental shortcoming: their absorption spectra are based on the forbidden 4f-4f transitions, and thus their absorption band in the ultraviolet-blue region is narrow and excitation efficiency is low, finally resulting in very weak near-infrared emissions from Yb3+ ions. Herein, our project will investigate the possibility of the Ag nanoclusters with intense absorption band in the 300-500 nm region as broadband sensitizer for these RE3+-Yb3+ downconversion couples. The proposed energy-transfer mechanism involves two-step processes: (1) Ag nanoclusters directly absorb a ultraviolet-blue photon and transfer the excited energy to RE3+ ions, and (2) the energy of the excited RE3+ ions is transferred to two different Yb3+ ions through downconversion, and thus intense near-infrared emissions can be achieved. We will focus on the fundamental investigation of the preparation method, optical properties, quantum efficiency, and luminescence dynamics of Ag and RE3+-Yb3+ co-doped fluorescent glasses. Then, we will discuss the mechanisms of the energy-transfer processes and downconversion luminescence, and finally establish the corresponding physical model. It is expected that this project could provide experimental data and theoretical base for the development and design of spectral conversion materials for solar cells, and thus could provide technological supports for fabricating high-efficiency crystalline-silicon solar cells.

以研究用于提高硅太阳能电池效率的新型银纳米簇宽带敏化稀土掺杂近红外下转换发光玻璃与器件所涉及的新原理、新材料与新工艺基础问题为目标。针对传统下转换稀土离子对RE3+-Yb3+（RE＝Tb, Pr, Tm, Ho, Er）对紫外光-蓝光光子吸收窄、吸收效率低和近红外发光弱的缺点，本项目拟以在300-500 nm波长范围具有宽带强吸收特性的银纳米簇为敏化剂，通过能量传递作用敏化RE3+离子，随后再通过稀土离子对RE3+-Yb3+的下转换发光过程，以期获得高转换效率的强近红外下转换发光。着重研究银纳米簇与稀土离子共掺杂发光玻璃的制备工艺、光谱特性、量子效率以及发光动力学行为。探讨能量传递和下转换发光机理，并建立相应的物理模型。本项目的研究将为探索与设计太阳能电池用新型高效光谱转换材料提供实验依据和理论指导，为开发高效硅太阳能电池提供技术支撑。

在国家青年科学基金项目（批准号51502190）的资助下，我们研究与开发了一系列稀土离子或者过渡金属离子掺杂光功能材料，主要成果如下：(1)开发了高灵敏的温度传感用上转换发光材料NaBiF4:Yb3+,Er3+。(2)开发了一系列高效、高热稳定性的新型植物照明用Mn4+掺杂红色荧光粉，例如：NaLaMgWO6:Mn4+、Ca3La2W2O12:Mn4+。(3)开发了新型高效Eu3+掺杂红色荧光粉（如：Na2Gd(PO4)(MoO4):Eu3+、NaBiF4:Eu3+），有望用于紫外激发白光LED器件。(4) 通过稀土离子间的能量传递，实现Tb3+-Eu3+掺杂荧光粉发光光谱的高效调控，可用于显示与白光LED等应用领域。(5) 基于基质材料-稀土离子或者稀土离子之间的能量传递作用，实现了单一白光荧光粉，如：LiCa3MgV3O12:Eu3+、 Ca3Y(GaO)3(BO3)4:Ce3+-Tb3+-Sm3+荧光粉。