基于金属离子掺杂低维铅卤钙钛矿光电性质研究

In the low-dimensional R-P lead halide perovskites (LDRPPs), the luminescence is dominated by exciton recombination. Its first-order exciton recombination can effectively compete with defect states trapping over a broad range of injected charge carrier densities, which make LDRPPs promising candidates for light emission applications. Nevertheless, the large exciton-phonon coupling strengths and lattice distortions inherent in soft LDRPPs could lead to the formations of bound-excitons, polarons, self-trapped excitons, and others. The dominant free exciton trapping and bound biexciton formation pathways that compete effectively with their band-edge recombination. As indicated by previous results, doping metal ions into halide perovskite host is considered as one of the most efficient methods, that enable to mitigate the lattice distortions and enhance the short-range lattice orders as well. In turn, it can improve the optoelectronic properties of perovskites. .In order to reveal these mechanisms and problems for further advances in light emission of these LDRPPs, we aim to synthesize a series of metal ions doped LDRPPs and propose to do a systematic charge carrier dynamics investigation on them with spatial-resolved ultrafast spectroscopy and micro-/nano-meter range morphology and composition analysis techniques. Constructing a direct correlation with doped metal ions, trap density, exciton-phonon interaction, multiexcitons (Auger recombination) and optoelectronic properties. Finally, we plan to establish a new strategy to precisely tune the optoelectrical properties in LDRPPs. Therefore, this research project will also contribute to the in-depth understanding and optimization of LDRPP based light emission applications.

低维Ruddlesden-Popper（R-P）铅卤钙钛矿室温下一阶的激子型复合发光使其在发光领域的应用极具潜力。然而低维R-P铅卤钙钛矿中铅卤八面体存在大幅度的晶格扭曲/畸变，引起束缚、极化子和自捕获激子的产生。这些辐射/非辐射复合过程往往不利于层状钙钛矿材料发光性质的改善，从而限制了其在高效率半导体器件的应用。研究结果表明，金属离子掺杂可以有效缓解钙钛矿主体晶格的畸变行为，稳定主体晶格结构，提高主体晶格短程的有序度，进而提高其光电性质。它为实现调控低维R-P钙钛矿光电性质提供了一种有效的途径。本项目拟制备获得一系列金属离子掺杂的层状钙钛矿材料；探究不同金属离子掺杂的层状铅卤钙钛矿中微纳结构、缺陷态、激子-声子耦合、Auger复合等因素与其光电性质存在的相互关联。构建金属离子掺杂的低维R-P铅卤钙钛矿的深层次光物理机制，以及提供调控钙钛矿半导体材料光电性的新方法和策略。

金属离子掺杂可以有效缓解钙钛矿主体晶格的畸变行为，稳定主体晶格结构，提高主体晶格短程的有序度，进而提高其光电性质。首先我们制备了一系列金属离子掺杂的钙钛矿材料；探究了不同金属离子掺杂的铅卤钙钛矿中微纳结构、光生载流子与其光电子性质的相互关联。在锌离子掺杂的CsPbI2Br钙钛矿薄膜中，实现了热载流子的冷却速率的调控；计算结果表明，在掺杂锌的钙钛矿中观察到的缓慢的热载流子弛豫可以归因于导带之间非绝热偶合的减少以及由锌掺杂剂引入的额外的弛豫通道，这会延迟光生热载流子的弛豫过程。其次，我们发现通过溴化钾掺杂三维以及低维钙钛矿材料，可以有效钝化钙钛矿表面缺陷，提升钙钛矿材料的发光效率；对于低维钙钛矿而言，溴化钾的加入可以触发多相钙钛矿晶粒向双层微结构的自组装，这主要是由于它作为异质成核模板在前体-基底底部界面上形成3钙钛矿晶粒。这种微结构使得更多的低n相倾向于转变为高n相和3D相，从而降低缺陷密度，促进电荷注入，并产生更多的发射中心。此外，底部3D层有利于空穴注入。因此KBr掺杂的 钙钛矿发光二极管实现了13.8%的高外量子效率和出色的重复性。