Stacking in Colloidal Nanoplatelets: Tuning Excitonic Properties
Stacking in Colloidal Nanoplatelets: Tuning Excitonic Properties
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DOI：
10.1021/nn5053734
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发表时间：
2014-12-01
期刊：
影响因子：
17.1
通讯作者：
Demir, Hilmi Volkan
中科院分区：
文献类型：
--
作者：
Guzelturk, Burak;Erdem, Onur;Demir, Hilmi Volkan
胶体半导体量子阱，通常也被称为纳米片（NPLs），已经成为最有前途的光产生和收获材料之一。最近，发现不良贷款堆积如山。然而，它们对这些应用至关重要的新特征以前没有被控制或理解。在本报告中，我们系统地研究和介绍了受控柱状NPL组件的激子性质。在这里，通过一个受控的渐进过程，我们证明了胶体量子阱中的堆叠大大增加了激子的转移和捕获。当不良贷款形成堆栈时，我们惊讶地发现它们的光致发光量子产率下降了一个数量级，而瞬态荧光衰减则大大加速。这些观测结果被堆叠NPLs中的超高效福斯特共振能量转移（FRET）证实，其中激子迁移估计在超长范围内（> 100nm）。研究发现，由于NPLs的共线取向紧密排列，消光系数大，Stokes位移小，从而产生了类似13.5 nm的大福斯特半径，因此在室温下，同质FRET（即相同发射器之间的FRET）的效率高达99.9%。因此，强而远的同质fret促进了非发射性不良贷款中的激子捕获，作为激子汇中心，由于被捕获的激子的快速非辐射重组，从堆叠的不良贷款中猝灭光致发光。基于速率方程的模型考虑了激子传递和堆内的辐射和非辐射复合，与实验数据吻合良好。这些结果显示了NPL固体中堆叠控制的关键意义，由于缺乏非均匀展宽，NPL固体与胶体纳米晶体表现出完全不同的均匀fret特征。
Colloidal semiconductor quantum wells, also commonly known as nanoplatelets (NPLs), have arisen among the most promising materials for light generation and harvesting applications. Recently, NPLs have been found to assemble in stacks. However, their emerging characteristics essential to these applications have not been previously controlled or understood. In this report, we systematically investigate and present excitonic properties of controlled column-like NPL assemblies. Here, by a controlled gradual process, we show that stacking in colloidal quantum wells substantially increases exciton transfer and trapping. As NPLs form into stacks, surprisingly we find an order of magnitude decrease in their photoluminescence quantum yield, while the transient fluorescence decay is considerably accelerated. These observations are corroborated by ultraefficient Forster resonance energy transfer (FRET) in the stacked NPLs, in which exciton migration is estimated to be in the ultralong range (>100 nm). Homo-FRET (i.e., FRET among the same emitters) is found to be ultraefficient, reaching levels as high as 99.9% at room temperature owing to the close-packed collinear orientation of the NPLs along with their large extinction coefficient and small Stokes shift, resulting in a large Forster radius of similar to 13.5 nm. Consequently, the strong and long-range homo-FRET boosts exciton trapping in nonemissive NPLs, acting as exciton sink centers, quenching photoluminescence from the stacked NPLs due to rapid nonradiative recombination of the trapped excitons. The rate-equation-based model, which considers the exciton transfer and the radiative and nonradiative recombination within the stacks, shows an excellent match with the experimental data. These results show the critical significance of stacking control in NPL solids, which exhibit completely different signatures of homo-FRET as compared to that in colloidal nanocrystals due to the absence of inhomogeneous broadening.