Hot Carrier Cooling Dynamics in Lead Halide Perovskite Nanomaterials
Ben Carwithen a, Thomas Hopper a, Ziyuan Ge a, Navendu Mondal a, Franziska Krieg b, Federico Montanarella b, Georgian Nedelcu b, Martin Kroll c, Karl Leo c, Yana Vaynzof c, Maryna Bodnarchuk b, Maksym Kovalenko b, Artem Bakulin a
a Department of Chemistry, Imperial College London, White City Campus, London, W12 0BZ, UK
b ETH Zurich, Laboratory of Inorganic Chemistry, Department of Chemistry & Applied Biosciences, Vladimir-Prelog-Weg, 1, Zürich, CH
c Integrated Centre for Applied Physics and Photonic Materials and Centre for Advancing Electronics Dresden (cfaed), Technical University of Dresden, Germany, Nöthnitzer Straße, 61, Dresden, Germany
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Oral, Ben Carwithen, presentation 051
Publication date: 20th April 2022

When a semiconductor is excited by a photon with energy greater than the material’s bandgap, the resulting “hot carrier” typically cools to the band edge on sub-ps timescales. Hot carrier cooling in halide perovskites is governed by the interplay of carrier-phonon and carrier-carrier interactions, and so the systematic study of their dynamics also reveals important underlying photophysical processes operating within these optoelectronic materials. This has generally been achieved using transient absorption and emission spectroscopic techniques, revealing phenomena such as the hot phonon bottleneck which slows hot carrier cooling at high carrier density. Disputes are still present on the effects of, for example, the composition, size and shape of the perovskite crystallites, partially due to the sophisticated analysis required to resolve various overlapping spectral features. To complement results from these methods, ultrafast pump-push-probe spectroscopy is presented here as a means of interrogating hot carrier dynamics in lead halide perovskite nanomaterials spanning a range of sizes and shapes. In cuboidal CsPbBr3 with side lengths of 5 nm, cooling dynamics are similar to their bulk analogue. However, 2D CsPbBr3 nanoplatelets and Ruddlesden-Popper (PEA)2PbI4 display considerably different behaviour, with a hot phonon bottleneck effect that becomes increasingly suppressed with greater excitonic character of the system. This is attributed to stronger Coulomb screening of carriers, which enhances the rate of cooling mediated by carrier-carrier scattering in low-dimensional perovskites.

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