Liu Mengxia, Verma Sachin Dev, Zhang Zhilong, Sung Jooyoung, Rao Akshay
Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Department of Emerging Materials Science, DGIST, Daegu 42988, Republic of Korea.
Nano Lett. 2021 Nov 10;21(21):8945-8951. doi: 10.1021/acs.nanolett.1c01892. Epub 2021 Nov 1.
Understanding carrier dynamics and transport in quantum dot based heterostructures is crucial for unlocking their full potential for optoelectronic applications. Here we report the direct visualization of carrier propagation in PbS CQD solids and quantum-dot-in-perovskite heterostructures using femtosecond transient absorption microscopy. We reveal three distinct transport regimes: an initial superdiffusive transport persisting over hundreds of femtoseconds, an Auger-assisted subdiffusive transport before thermal equilibrium is achieved, and a final hopping regime. We demonstrate that the superdiffusive transport lengths correlate strongly with the degree of energetic disorder and carrier delocalization. By tailoring the perovskite content in heterostructures, we obtained a superdiffusive transport length exceeding 90 nm at room temperature and an equivalent diffusivity of up to 106 cm s, which is 4 orders of magnitude higher than the steady-state values. These findings introduce promising strategies to harness nonequilibrium transport phenomena for more efficient optoelectronic devices.
了解基于量子点的异质结构中的载流子动力学和输运对于释放其在光电器件中的全部潜力至关重要。在此，我们报告了使用飞秒瞬态吸收显微镜对PbS量子点固体和钙钛矿量子点异质结构中载流子传播的直接可视化。我们揭示了三种不同的输运机制：持续数百飞秒的初始超扩散输运、在达到热平衡之前的俄歇辅助亚扩散输运以及最终的跳跃机制。我们证明超扩散输运长度与能量无序程度和载流子离域化密切相关。通过调整异质结构中的钙钛矿含量，我们在室温下获得了超过90 nm的超扩散输运长度和高达106 cm² s的等效扩散率，这比稳态值高4个数量级。这些发现引入了有前景的策略，以利用非平衡输运现象来制造更高效的光电器件。
