On the Determination of Carrier Temperature in Direct Band Gap Semiconductors

Ivo Tanghe^a^,^b^,^c, Isabella Wagner^d^,^e^,^f^,^g, Servet Ataberk Cayan^b^,^c, Dries Van Thourhout^a, Justin Hodgkiss^d^,^e^,^f^,^g, Kai Chen^d^,^e^,^f^,^g, Pieter Geiregat^b^,^c

^aPhotonics Research Group, Ghent University, Belgium, Technologiepark-Zwijnaarde, 126, Gent, Belgium

^bPhysics and Chemistry of Nanostructures, Department of Chemistry, Ghent University, Ghent, Belgium

^cNoLIMITS Center for Non-Linear Microscopy and Spectroscopy, Belgium, Ghent University, Gante, Belgium

^dSchool of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand, PO Box 600, Wellington, New Zealand

^eMacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand., PO Box 600, Wellington, New Zealand

^fRobinson Research Institute, Victoria University of Wellington, Wellington, New Zealand, PO Box 600, Wellington, New Zealand

^gThe Dodd-Walls Centre for Photonic and Quantum Technologies, University of Otago, PO Box 56, Dunedin, New Zealand

Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS23 & Sustainable Technology Forum València (STECH23) (MATSUS23)

#NCFun23 - Fundamental Processes in Nanocrystals and 2D Materials

VALÈNCIA, Spain, 2023 March 6th - 10th

Organizers: Valerio Pinchetti and Shalini Singh

Oral, Ivo Tanghe, presentation 158
DOI: https://doi.org/10.29363/nanoge.matsus.2023.158
Publication date: 22nd December 2022

When studying the opto-electronic properties of (nanostructured) semiconductors, Transient Absorption (TA) or pump-probe spectroscopy is often used to measure ultrafast changes optical properties due to photo-excitation. Besides making direct conclusions on carrier recombination processes, quantification of net optical gain or studying photo-induced absorption, a typical analysis that is done on such datasets is a Boltzmann fit on the high-energy tail from which the temperature of the photo-excited charge carriers can be extracted. Such information is vital in understanding carrier cooling bottlenecks which are detrimental for optical gain applications, but potentially very useful in solar energy conversion. Usually, this extraction of temperature is done for different pump-probe delays, excitation energies and different excitation powers to see the impact on the thermalization of the carriers.¹ In this work, we take a more detailed look at what this high-energy tail actually entices for a direct gap semiconductor. We show that within this simple fitting approach, one gravely overestimates carrier temperatures and propose a more consistent modelling to find the temperature. Next, we compare this approach to Ultrafast Photoluminescence (UFPL) measurements on the same timescales as TA. We show that extracting the temperature is a more straightforward process for this approach.

References:

[1] 1) Geiregat, Pieter, et al. "Using bulk-like nanocrystals to probe intrinsic optical gain characteristics of inorganic lead halide perovskites." ACS nano 12.10 (2018): 10178-10188.

Acknowledgements:

I.T. Acknowledges FWO-Vlaanderen for a PhD Fellowship.

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