Ultrafast Spectroscopy of Perovskite Nanostructures
Tönu Pullerits a, Kaibo Zheng a b, Ziqi Liang c
a Chemical Physics and NanoLund, Lund University, P.O. Box 124, 22100 Lund, Sweden
b Danish Technical University
c Department of Material Science, Fundan University
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference on Perovskite and Organic Photovoltaics and Optoelectronics (IPEROP19)
Kyōto-shi, Japan, 2019 January 27th - 29th
Organizers: Hideo Ohkita, Atsushi Wakamiya and Mohammad Nazeeruddin
Invited Speaker, Tönu Pullerits, presentation 032
DOI: https://doi.org/10.29363/nanoge.iperop.2019.032
Publication date: 23rd October 2018

Nano-size semiconductor structures have a reach spectrum of properties related to quantum confinement which are not available in the corresponding bulk materials. Size-tuneable spectrum is, perhaps, the best known and understood such property. Here we investigate dissipation and transport dynamics of various semiconductor nanosystems and their composites. We have studied colloidal quantum dots, plasmonic metal nanoparticles, hybrid and all inorganic perovskite nanocrystals and Ruddlesden–Popper 2D perovskites. We apply a set of modern ultrafast techniques like photocurrent and fluorescence detected coherent 2D spectroscopy, transient terahertz and absorption spectroscopies revealing detailed information about photoexcitation dynamics.

As an example [1]. Photo-generated charge carrier dynamics in Ruddlesden-Popper 2D perovskites with linear (n-BA) and branched (iso-BA) butylamine as spacing cations were studied by using transient absorption and time-resolved photoluminescence spectroscopies. Both n-BA and iso-BA perovskites consist of mixed-phase 2D quantum wells with various layer thicknesses, where the photo-generated charges undergo inter-phase charge transfer from thinner quantum wells to thicker ones. By shortening the spacer from n-BA to iso-BA, the transfer rates are significantly increased, which can also diminish the charge accumulation in thin quantum wells induced by the unbalanced electron and hole charge transfer rates. Under high excitation intensity, the shorter spacing cation is found to further facilitate transport, which can compete with fast high-order carrier recombination and consequently improve the charge transfer efficiency. Intriguingly, we observe the existence of extra bulk 3D phases embedded within iso-BA perovskites, which can efficiently collect the confined charges within 2D phases and then transport them with faster carrier mobility and slower recombination rates.

We acknowledge financial support by the Swedish Research Council, KAW Foundation, Swedish Energy Agency and STINT. Z. L. thanks the support from Inter-Governmental International Cooperation Projects of Science and Technology Commission of Shanghai Municipality (STCSM) under grant no. 17520710100.

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