稀土掺杂非计量比氮化硅薄膜的能量传递机理及量子剪裁应用

Quantum cutting approach is a good way to improve photovoltaic efficiency of crystalline silicon solar cell. The traditionally used phosphor or class ceramic as downconversion matrix is, however, not compatible to silicon lattice. Thus, the investigation on new matrix is of great importance. Non-stoichiometric silicon nitride materials (SiNx) have some sensitizers towards rare earth (RE) ions, greatly enhancing the RE emission intensity. This proposal will study on the energy transfer mechanism in SiNx layers doped by RE ions (Tb3+-Yb3+ or Pr3+-Yb3+) quantum cutting in solar cell. The layers will be deposited by magnetron sputtering using N2 and Ar to generate plasma. During sputtering, nitrogen will react with silicon to form silicon nitride. The Si/N ratio and RE ions concentration will be tuned by N2/Ar and targets power. The micro-structures will be optimized via an annealing process to enhance sensitizers density for high emission intensity. This work will focus on energy transfer mechanisms between matrix sensitizers and RE ions, as well as their influence on quantum efficiency. The optimized layer will be deposited on silicon solar cell to approach our goal of high photovoltaic efficiency. Such work results will promote the fundamental research and future applications of novel downconvesion SiNx layers.

量子剪裁是提高硅太阳能电池效率的一条有效途径。传统的磷光体、玻璃陶瓷等下转换层基底材料，与硅电池材料晶格不匹配兼容，研发新型的基底材料具有重要意义。非计量比氮化硅具有多种敏化剂，可极大提高掺杂稀土离子的发光性能。本项目拟研究稀土(Tb3+-Yb3+，Pr3+-Yb3+) 掺杂SiNx薄膜材料的能量传递机理及其该类下转换层在太阳能电池中的应用。利用磁控溅射法制备薄膜材料，即通入N2和Ar气体产生等离子体，溅射靶材过程中氮与硅反应生成氮化硅。改变不同靶材功率和通入气体比值，调节基底Si/N比值和掺杂稀土离子浓度。利用热处理工艺优化薄膜样品微观结构，增加基底敏化剂密度，测量发光性质。重点研究基底敏化剂与稀土离子的能量传递机理及其对稀土离子体系量子效率的影响规律。通过对沉积最优下转换层薄膜的太阳能电池进行光电性能测试，实现提高转换效率的目标。研究成果将为新型光电转换材料的的研究和实际应用奠定基础。

有效利用太阳能是解决能源危机的一个重要途径。目前应用广泛的硅基太阳能电池光电转换效率低。利用量子剪裁可修饰太阳光谱，减少高能光子的能量损失，借以提高硅基太阳能电池的光电转换效率。非计量比氮化硅相比磷光体、硼酸盐、氟化物等材料，与电池硅晶体匹配性更好。特别是非计量比氮化硅材料中的敏化剂可对稀土离子进行有效激发，使稀土离子的有效激发截面增加几个数量级，发光强度大大增强。.本项目利用磁控溅射法，设计沉积了富氮的氮氧化硅和富硅的氮氧化硅两种基底材料，研究了沉积工艺、等离子体气体比例、退火温度等因素对样品结构以及发光性能的影响。系统研究了不同单掺杂体系中所掺杂的稀土离子种类及其掺杂浓度对发光性能的影响。对其发光机理进行了深入探讨。硅纳米颗粒、缺陷、带尾等都是基底中的敏化剂，可传递能量给稀土离子。探索了近红外量子剪裁纳米材料在提高硅太阳能电池光电转换效率方面的应用：获得的近红外量子剪裁薄膜，有效地实现了1000 nm左右的近红外光发射，这一发射波长与硅基太阳能电池的硅带隙相匹配，将其用于硅太阳能电池的光转换层，可有效减少硅太阳能电池因光谱失配造成的能量损失，提高硅太阳能电池的光电转换效率。