Hot Carrier Recombination in Lead Halide Perovskite Nanocrystals
Paris Papagiorgis a, Andreas Manoli a, Caterina Bernasconi b c, Maryna I. Bodnarchuk b c, Maksym V. Kovalenko b c, Andreas Othonos d, Grigorios Itskos a
a Department of Physics, Experimental Condensed Matter Physics Laboratory, University of Cyprus, Nicosia 1678, Cyprus
b Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093 Zürich, Switzerland
c Laboratory for Thin Films and Photovoltaics, Empa – Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
d Department of Physics, Laboratory of Ultrafast Science, University of Cyprus, Nicosia 1678, Cyprus
nanoGe Fall Meeting
Proceedings of nanoGe Fall Meeting19 (NGFM19)
#NCFun19. Fundamental Processes in Semiconductor Nanocrystals
Berlin, Germany, 2019 November 3rd - 8th
Organizers: Ivan Infante and Jonathan Owen
Poster, Paris Papagiorgis, 372
Publication date: 16th July 2019

Lead halide perovskite nanocrystals (LHP NCs) have recently emerged as promising light emitters due to their efficient, narrow and tunable luminescence and their attractive optical gain properties. Further to such attributes, an efficient slowdown of the hot carrier cooling makes such NCs, promising for hot carrier solar cells. Recent work have studied the relaxation mechanisms of hot carriers in LHP NCs, yet the influence of the prolonged carrier cooling on the radiative recombination under sufficiently high photoexcitation that allow both spontaneous and stimulated emission to occur, has not been investigated.  

Herein we present an optical study of the properties of hot electron-hole gases in three representative LHP NCs based on the inorganic CsPbBr3 and the hybrid FAPbBr3 and FAPbI3 materials [1]. We employ a series of optical experiments in the high excitation density regime, where the carrier occupancy per NC is larger than 1 and probe the nature and characteristics of the carrier recombination from the steady state to the femtosecond regime. In all NC systems, evidence of slow hot carrier cooling is observed with the carrier relaxation appearing further pronounced in the FAPbI3 NCs, in agreement with previous work performed within the low excitation regime [2]. By extending the work to significantly higher fluences where the number of carriers per NC is larger than 2, the impact of hot carriers on the emission becomes evident, resulting in some cases in an oscillatory transient behavior and suppression of the amplified spontaneous emission (ASE) in favor of higher energy emission from hot carriers. We probe the energetics and dynamics of such competition and unravel the impact of experimental and material factors such as temperature, film quality and excitation pulse duration and wavelength.

We acknowledge financial support from the Research Promotion Foundation of Cyprus, under the "NEW STRATEGIC INFRASTRUCTURE UNITS- YOUNG SCIENTISTS" Programme (Grant Agreement No. "INFRASTRUCTURES/1216/0004", Grant "NANOSONICS")

© Fundació Scito
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