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Photoexcited Ultrafast Dynamics of Free Carriers and Polarons in V2O5 Microparticles through Time-Resolved Nondegenerate Pump Probe Spectroscopy (Dr. Kamaraju Natarajan )

V2O5 is a very promising material with a wide range of applications, including light harvesting, energy storage, photocatalysis, photodetectors, solar cells, light-emitting diodes, and wave guides. However, for optimal device performance as well as from a fundamental physics point of view, a proper understanding of carrier dynamics in V2O5 based systems is essential. Despite such huge potential, not much time resolved experiments were performed on these materials, leaving the ultrafast dynamics obscure. This article is focused to unravel the ultrafast dynamics of photo-excited carriers in V2O5 microparticles. We have used time-resolved non-degenerate pump-probe transmission spectroscopy to investigate the photo-excited carrier dynamics in V2O5 microparticles. Tri exponential function has been used to fit the time-resolved absorption data derived from transient transmission data. A closer look utilizing pump fluence-dependent analysis reveals that the decay is considerably impacted by the pump fluence, indicating that fitting with first order decay process is insufficient to explain the decay dynamics. To understand further, a numerically solved first order coupled differential equations based polaronic kinetic model is used on the time-resolved absorption data to study the formation of polarons and their various decay channels. Through this analysis, it is found that the free carriers are trapped in polaronic traps within an average time scale of ~4.5ps, and these polarons subsequently interact with the free carriers to undergo polaron-assisted bi-molecular decay. Using the pump fluence-dependent experiments, the variation of the various underlying processes could be explained through the carrier screening concepts. It is estimated that the average density of polarons here, is ∼2.58×1017cm−3 in our study.

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Posted on: April 21st, 2023