Effect of Connectivity on the Carrier Transport and Recombination Dynamics of Perovskite Quantum-Dot Networks [Dataset]

Quantum-dot (QD) solids are being widely exploited as a solution-processable technology to develop photovoltaic, light-emission, and photodetection devices. Charge transport in these materials is the result of a compromise between confinement at the individual QD level and electronic coupling among the different nanocrystals in the ensemble. While this is commonly achieved by ligand engineering in colloidal-based systems, ligand-free QD assemblies have recently emerged as an exciting alternative where nanostructures can be directly grown into porous matrices with optical quality as well as control over their connectivity and, hence, charge transport properties. In this context, we present a complete photophysical study comprising fluence- and temperature-dependent timeresolved spectroscopy to study carrier dynamics in ligand-free QD networks with gradually varying degrees of interconnectivity, which we achieve by changing the average distance between the QDs. Analysis of the photoluminescence and absorption properties of the QD assemblies, involving both static and timeresolved measurements, allows us to identify the weight of the different recombination mechanisms, both radiative and nonradiative, as a function of QD connectivity. We propose a picture where carrier diffusion, which is needed for any optoelectronic application and implies interparticle transport, gives rise to the exposure of carriers to a larger defect landscape than in the case of isolated QDs. The use of a broad range of fluences permits extracting valuable information for applications demanding either low- or high-carrier-injection levels and highlighting the relevance of a judicious design to balance recombination and diffusion.

量子点（Quantum-dot, QD）固体作为一种可溶液加工的技术，被广泛用于开发光伏、发光及光电探测器件。这类材料中的电荷输运，是单个量子点层面的限域效应与集合体内不同纳米晶间的电子耦合共同作用的结果。在传统胶体基体系中，这一平衡通常通过配体工程实现；而无配体量子点组装体近来成为极具潜力的替代方案，其纳米结构可直接生长于多孔基质中，兼具光学品质，且可精准调控其连通性与电荷输运特性。在此背景下，本研究开展了一套完整的光物理研究：采用注量与温度依赖的时间分辨光谱技术，对连通性呈梯度变化的无配体量子点网络中的载流子动力学展开探究——我们通过调控量子点间的平均距离来实现连通性的梯度调控。对该量子点组装体的光致发光与吸收特性开展静态与时间分辨测试后，我们得以明确不同辐射及非辐射复合机制的占比如何随量子点连通性发生变化。本研究提出了如下机制：相较于孤立量子点，任何光电子应用所需的载流子扩散（即粒子间输运过程）会使载流子暴露于更大范围的缺陷环境中。通过调控宽泛的注量范围，本研究可为需求不同载流子注入水平的光电子应用提供有价值的参考，并凸显出合理设计以平衡复合与扩散过程的重要性。