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

^aExperimental Condensed Matter Physics Lab, Department of Physics, University of Cyprus, Cyprus

^bETH Zurich, Laboratory of Inorganic Chemistry, Department of Chemistry & Applied Biosciences, Vladimir-Prelog-Weg, 1, Zürich, Switzerland

^cEMPA - Swiss Federal Laboratories for Materials Science and Technology, Überland Strasse, 129, Dübendorf, Switzerland

^dLaboratory of Ultrafast Science, Department of Physics University of Cyprus, Nicosia, Cyprus

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Fall Meeting19 (NFM19)

#NCFun19. Fundamental Processes in Semiconductor Nanocrystals

Berlin, Germany, 2019 November 3rd - 8th

Organizers: Ivan Infante and Jonathan Owen

Poster, Paris Papagiorgis, 372
Publication date: 18th 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.

References:

[1] Papagiorgis P.; Manoli A.; Michael S.; Bernasconi C.; Bodnarchuk M. I.; Kovalenko M. V.; Othonos A.; Itskos G. Unraveling the Radiative Pathways of Hot Carriers upon Intense Photoexcitation of Lead Halide Perovskite Nanocrystals, ACS Nano,2019,13,5,5799-5809

[2] Papagiorgis P.; Protesescu, L.; Kovalenko M. V.; Othonos, A.; Itskos, G., Long-lived hot carriers in formamidinium lead iodide nanocrystals, J. Phys. Chem. C , 2017, 121, 12434−12440.

Acknowledgements:

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")

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