核壳结构全无机钙钛矿量子点微纳激光增益机理及器件研究

With the advantages of low cost, facile fabrication, low threshold, tunable emission, and high optical gain, mirco/nanolasers based on all-inorganic perovskite quantum dots (QDs) have splendid prospects in future integrated optoelectronics and other related fields. However, their further practical application are seriously blocked by the nonradiative Auger recombination and poor stability suffered from water and air. To overcome these challenges, in our project, we will at first fabricate the first core/shell structured colloidal perovskites QDs by combining II-VI nanocrystals with all-inorganic perovskite QDs. By capping each individual all-inorganic perovskite QD with nanocrystal shell such as CdS , the nonradiative Auger recombination of as-grown core/shell QDs is expected to be suppressed, and chemical stability will be improved due to the protective shells that isolate the QDs from moisture in the air. Then, we apply femtosecond transient absorption spectroscopy to study the the optical gain dynamics and charge transfer process between the perovskite core and II-VI nanocrystal shell of encapsulated perovskite QDs, which will provide insightful understanding of some fundamental mechanisms, such as the suppression mechanism of the noradiative Auger recombination, the optical gain formation of quantum dots, and the competition between the radiation and nonradiation processes. From this kind of study, we can further explore the effective way to improve the performance of the lasers. At last, base on the materials and mechanism studies, we will design and prepare different types of micro/nano lasers by incorporating the inorganic core/shell structured perovskite QDs with differenct micro/nanostructures, and study their performances under different experimental conditions to optimize their laser performance devices. Consequently, perovskite micro/nano lasers with excellent performances and long-term stability are realized. We hope the results achieved in our project could promote future nanophotonic exploration and the practical application and commercialization process of the all-inorganic perovskite based mirco/nanolasers.

基于钙钛矿量子点的微纳激光器件具有成本低廉、工艺简单、阈值低、带隙可调、光学增益高等优点，在未来集成光电子学等领域有巨大应用前景，然而，钙钛矿量子点的非辐射俄歇复合及遇水、空气易分解等问题严重影响着微纳激光器件的性能提升及工作寿命。为解决这些问题，本项目将主要开展以下研究：使用CdS等II-VI族纳米晶对全无机钙钛矿量子点进行包覆，制备核壳结构的钙钛矿量子点，有效抑制俄歇复合及提升材料稳定性；利用飞秒瞬态吸收光谱研究钙钛矿量子点核与II-VI族纳米晶壳之间的电荷转移等过程，挖掘非辐射跃迁抑制机理及钙钛矿激光增益产生机理，分析辐射与非辐射跃迁的超快竞争机制，进一步探索寻找提升激光性能的有效途径；在材料与机理研究的基础上，设计、制备不同腔型的微纳激光器，研究它们在不同实验条件下的微激光性能并加以优化，最终实现具有优异激光性能与工作稳定性的钙钛矿微纳激光器件，进一步推动它们的实用化和商品化进程。

钙钛矿量子点的非辐射俄歇复合以及遇水、空气分解等问题严重影响着钙钛矿微纳激光器件的性能提升及工作寿命。如何提升钙钛矿发光稳定性及激光器件性能是本领域的关键因素，同时探索和揭示钙钛矿作为增益介质的受激辐射机制是沟通钙钛矿材料和器件性能之间的桥梁。本项目通过对钙钛矿材料改性、机理研究、器件发展等角度全方位的探索研究提升钙钛矿量子点及相关微纳激光器件发光性能及稳定性的有效途径。取得的主要成果如下：1）成功制备了首个具有单核壳结构的全无机CsPbX3 钙钛矿量子点，通过CdS壳层的包覆，阻止了量子点内部电子逃逸的过程，有效抑制了量子点的“闪烁”效应，减弱了量子点的非辐射俄歇复合，同时稳定性在高温、高湿环境得到有效提升，实现了相对发光的增强及单光子/双光子放大自发辐射阈值的有效降低，并首次实现了钙钛矿类核壳结构量子点的低阈值的回音壁模式激光稳定输出；2）通过超快激光光谱技术，揭示了极化子的存在、增益寿命、能量转移过程等对不同维度钙钛矿受激辐射的影响机制。3）进一步开发了新型多维度调控的钙钛矿微纳激光器件，实现了优异激光性能与工作稳定性的零维、二维、准二维钙钛矿等微纳激光稳定输出，特别是在深亚波长尺度（~50 nm）实现了高性能小型化钙钛矿激光器。本项目的实施为设计和研制高性能钙钛矿微纳激光器件提供了重要的参考，对钙钛矿实用化具有重要意义。