稀土/全无机钙钛矿核壳纳米晶的电子结构与光学性能

Rare-earth-doped (RE-doped) luminescent nanomaterials have advantages of sharp emission peaks, long lifetime, and high photo-stability. However, the weak luminescence intensity and low luminescence efficiency problem limits the practical applications of RE-doped nanomaterials. It is expected to achieve high luminescence efficiency of RE ions through all inorganic perovskite quantum dots (PeQDs) sensitization by making use of large absorption cross-section of all inorganic PeQDs. At present, RE-doped all inorganic PeQDs suffer the energy level mismatch and cross relaxation between RE ions and PeQDs, resulting in the low luminescence efficiency of RE ions. In this project, we aim to develop the highly emissive composite based on the NaGdF4:Sm3+ (or Dy3+)@CsPbX3 (X=Cl or Br) core-shell nanocrystals through PeQDs sensitization. The surface engineering treatment of RE-doped nanocrystals and solvothermal method is used to epitaxial growth core-shell nanocrystals. To improve the energy transfer efficiency between PeQDs and RE-doped nanocrystals through matching the gap of PeQDs and energy level of RE ions. The energy transfer mechanism between RE-doped nanocrystals and PeQDs will be investigated by using low-temperature high resolution spectroscopy and transient absorption spectroscopy. The luminescence intensity of composites is expected to improve by orders of magnitude and the photoluminescence quantum yield is larger than 60%, and the results of this project will play an important role in the field of lighting and displays, and biomedicine.

稀土掺杂纳米发光材料具有发射谱线窄、荧光寿命长及发光稳定性好等优点，但发光强度弱、发光效率低的问题制约了其实际应用。利用全无机钙钛矿量子点大的吸收截面，通过钙钛矿敏化稀土离子有望提高其发光效率。目前，稀土掺杂的全无机钙钛矿量子点存在稀土离子与钙钛矿量子点能级不匹配及交叉弛豫的问题，导致稀土离子发光效率低。本项目致力于研发具有高效敏化稀土离子发光的稀土/全无机钙钛矿NaGdF4:Sm3+ (或Dy3+)@CsPbX3 (X=Cl或Br)核壳纳米晶，采用稀土纳米晶的表面工程处理及溶剂热法外延生长复合材料；调节钙钛矿量子壳层的带隙与稀土离子能级相匹配，提高钙钛矿与稀土纳米晶的能量传递效率；利用低温高分辨光谱和瞬态吸收光谱揭示稀土纳米晶与全无机钙钛矿量子壳层的能量传递机理。预期研制的稀土复合材料发光强度实现数量级的提升且发光绝对量子产率高于60%，有望在照明显示和生物医学等领域发挥重要作用。

全无机钙钛矿因其优异的光学性能，在光电和光伏领域显示出巨大的应用潜力。本项目利用离子掺杂策略来提高全无机无铅钙钛矿的荧光量子产率并揭示了其激发态动力学。通过Sb3+掺杂实现对0D A2InX5·H2O及A3InX6(A = Cs和Rb; X = Cl和Br)晶体的光学性能调控，并揭示了Sb3+的激发态动力学。该0D铟基卤化物表现出高效的宽带发射和较大的斯托克斯位移。基于A位阳离子和八面体配位的调控，实现了从490到750 nm可调的宽带发射，其最高荧光量子产率为91.8%。该研究为Sb3+掺杂0D金属卤化物的激发态动力学提供了新的见解，为新型高效的离子掺杂0D金属卤化物的设计开发及应用奠定了基础。此外，通过铜离子（Cu+）掺杂实现了Cs2(Ag/Na)InCl6的高效自陷激子发光。通过少量Cu+掺杂（1.0 mol%）显著提高了自陷激子的发射，将其荧光量子产率从19.0%提升到62.6%，同时其激发峰从310 nm红移到365 nm。进一步的变温荧光光谱和超快飞秒瞬态吸收光谱研究表明，发光显著增强源自Cu+掺杂导致自陷激子波函数对称性降低，引起自陷激子态密度和辐射复合速率的增加。该研究为离子掺杂Cs2(Ag/Na)InCl6中自陷激子的激发动力学提供了深入的理解，从而为设计高效自陷激子发射的无铅双钙钛矿奠定了基础。