Proceedings of MATSUS23 & Sustainable Technology Forum València (STECH23) (MATSUS23)
DOI: https://doi.org/10.29363/nanoge.matsus.2023.004
Publication date: 22nd December 2022
Photoexcitation of semiconductors by photons of higher energy than the bandgap creates ‘hot-charge carriers’ (i.e. different thermal energy w.r.t. lattice), which further cool down to the band-edge state by releasing their excess energy as a waste form of heat. Harvesting the excess energy of these hot carriers (HC) could eventually boost the performance of solar cells by manifold, while practical realization of this is still limited owing to the rapid cooling of these HC [1, 2]. On the contrary, in light-emitting applications, rapid HC cooling is highly desired to enable efficient radiative recombination by preventing carrier trapping. Therefore, detailed understanding of the HC cooling mechanisms and further controlling their dynamical pathways is prerequisite for engineering the semiconductor optoelectronics.
Herein I will explore this key area on CsPbX3 perovskite nanostructures of various dimensions and compositions by employing novel pump-push-probe based transient spectroscopy [3], which provides direct access to selectively control the hot carrier density and study their influence. This experimental finding unravels the role of carrier-carrier, carrier-phonon interactions to carrier-impurity (defect) scatterings in tailoring the hot carrier cooling dynamics in perovskite nanosystems. Our results of HC cooling dynamics among halide-composition space with controlled defect densities reveals that this dynamics is defect-tolerant for pure-iodide based perovskites unlike pure-Br and mixed (Br/I)-systems. Importantly, we also examine the slowing down pattern of HC cooling dynamics under high HC-density (termed as hot-phonon bottleneck effect), whose effect is significantly suppressed with the increase in quantum confinement (from 3D to 2D systems) due to reduced screening by phonons and enhanced Coulombic interaction between electron and holes for the latter systems. Although halide-vacancy related defects accelerate the HC cooling dynamics for pure Br-and mixed (Br/I)-systems, but they do not induce any such effect on the hot-phonon bottleneck process possibly due to saturation of the trap-states. This detailed understanding of the key routes that control the HC cooling dynamics would be instrumental for prospective applications of the next-generation perovskite optoelectronics.
N.M. and A.B. acknowledge support from the European Commission through the Marie Skłodowska-Curie Actions (Project PeroVIB, H2020-MSCA-IF-2020-101018002).
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