Rashba effect as a source for a long carrier diffusion length in nanostructures assembly and bulk halide perovskites
Alyssa Kostadinov - Mutzafi a, Maya Isarov a, Liang Zheng Tan b, Andrew Rappe b, Efrat Lifshitz a
a Technion - Israel Institute of Technology, Haifa, Israel
b University of Pennsylvania, 200 South 33rd Street, Philadelphia, 19104, United States
nanoGe Perovskite Conferences
Proceedings of International Conference on Perovskite Thin Film Photovoltaics, Photonics and Optoelectronics (ABXPV18PEROPTO)
Perovskite Photonics and Optoelectronics (PEROPTO18). 1st March
Rennes, France, 2018 February 27th - March 1st
Organizers: Jacky Even and Sam Stranks
Oral, Alyssa Kostadinov - Mutzafi, presentation 024
DOI: https://doi.org/10.29363/nanoge.abxpvperopto.2018.024
Publication date: 11th December 2017

During the past few years, hybrid organic-inorganic perovskites have become one of the most promising materials in the photovoltaic field, when in less than four years, the efficiency of perovskite solar cells has quickly leapt from 3.81% to > 22.0%. Perovskites have also been demonstrated as suitable materials for detecting visible light, x-ray, or γ-ray.

The talk will include description of a research work associated with all-inorganic bromide- perovskite, CsPbBr3, as nanocrystals and bulk forms.  This compound was selected for the study due to its relative chemical and photochemical stability.  The nature of carriers at the excited state were investigated by following the interplay of Rashba and band-edge exciton effects in a single colloidal nanocrystals (NCs) or a single bulk specie.  The samples were supplied by the group of Prof. Maksym Kovelenko at ETH. In a single NC, pronounced evidence for the Rashba effect in the excitonic magneto-photoluminescence spectra was observed.  It was measured via examination of the linearly and circularly polarized photoluminescence of a single particle under an applied magnetic field. The experiments resolve discrete narrow excitonic transitions with an energy splitting that increases nonlinearly with the magnetic field strength. The nonlinearity in the exciton photoluminescence (PL) splitting observed in the experiment is supported by theoretical calculations (in collaboration with the group of Prof. Andrew Rappe), suggesting a crossover between the Rashba effect at low magnetic fields to a Zeeman effect at higher fields.  Current observations on bulk CsPbBr3 single crystal, reflect similar observations for those viewed in the analogous NCs, particularly when examined along unique crystallographic direction.  In addition, the observations found in the bulk samples indicate a plausible contribution of cubic Rashba effect, which may indicate a mixing of high lying states to the band-edge properties. The Rashba effect splits the band edge extrema to a k¹0 a Brillouin point with momentum forbidden transitions, thus, extending the carriers lifetime at the excited state.  It is currently proposed that the Rashba effect is one of the main sources that endows a long diffusion length for carriers in perovskites materials.

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