高稳定CsPbBr3核壳结构钙钛矿量子点的激光特性研究

All-inorganic perovskite quantum dot (QD) lasers have promising potential applications in the field of optical quantum-communication. Suppression of ultrafast Auger recombination by core-shell structures to prolong the optical-gain lifetimes in QDs is the key to optimize the performance of perovskite QD laser. The CsPbBr3 perovskite QDs are embedded in Cs4PbBr6 crystals to form high quality core-shell like composites to understand the influence of size, surface defect, doping concentration and other factors on the photoluminescence spectra and efficiency of the QDs. The effect of energy transfer among QDs on self-quenching will be investigated by means of steady-state and time-resolved spectroscopy. The effect of QD surface defect and size on the Auger recombination will be studied to understand the optical-gain and lasing regime as well as to explore the way to suppress the Auger recombination. High quality QD lasers will be fabricated based on the CsPbBr3@Cs4PbBr6 core-shell perovskite composites. The laser modes and polarization will be flexibly modulated by controlling the size and morphology of the Cs4PbBr6 matrix shell. Researches on these basic physical mechanisms will have important scientific significance for the performance improvement and practical application of QD lasers.

全无机钙钛矿量子点激光器在光量子通讯领域具有潜在的应用前景。利用核壳结构抑制量子点增益介质中的俄歇复合过程，延长光增益寿命是获得高性能钙钛矿量子点激光器的关键。基于量子点核壳结构原理，将CsPbBr3量子点嵌入Cs4PbBr6晶体中构筑高效发光的类核壳结构纳米材料，理解量子点的尺寸、表面缺陷、嵌入密度与发光性质之间的关系。利用稳态与瞬态光谱技术分析嵌入密度对CsPbBr3量子点间的激子能量传递过程的影响，研究CsPbBr3量子点表面缺陷和尺寸对俄歇复合过程的影响，揭示其中光增益和受激辐射机理，有效抑制量子点中俄歇复合过程。制备基于CsPbBr3@Cs4PbBr6核壳结构的量子点激光器，研究Cs4PbBr6壳层材料的尺寸和结构对激光输出的影响，获得模式可控的高效全无机钙钛矿量子点激光器。预计上述基础物理问题的研究，将对钙钛矿量子点激光器的性能改善和实际应用具有重要的科学意义。

全无机钙钛矿量子点激光器在近红外生物成像和光量子通讯领域具有潜在的应用前景，但是，目前高的泵浦阈值带来的的稳定性问题一直限制其进一步的实际应用化推广。我们合成了高效发光的钙钛矿量子点，基于激子跃迁选择规则和量子力学计算，并结合单光子、双光子和三光子吸收光谱来确定了量子点中允许的激子跃迁，结果表明在共振激发模式下，获得的量子点激光器泵浦阈值最低。通过超快瞬态吸收光谱技术，我们清楚地观察到CsPbBr3量子点光增益建立的动力学过程，并确认光增益寿命可以达到18 ps。确认了量子点中双激子复合和非辐射衰减速率对于激光发射的影响，证明了量子点中所观察到的双激子激光发射的普遍性。基于聚合物溶液表面张力效应，对微球谐振腔的制备进行调控得到了不同粒径的微球谐振腔，获得了高稳定的多模和单模的激光发射。最后，提出CsPbBr3量子点的双光子和三光子的光吸收可以通过将激发光能量与激子共振匹配而得到显著增强，从而获得高稳定和低泵浦阈值的多光子激光发射。在项目资助下，共发表SCI论文6篇，申请授权国家发明专利1项。