Photoemission Studies of Rashba and Polaronic Effects in Halide Perovskites
Maryam Sajedi a b, Maxim Krivenkov a, Dmitry Marchenko a, Jaime Sánchez-Barriga a, Anoop Chandran c d, Andrei Varykhalov a, Emile Rienks a, Irene Auilera e, Stefan Blügel c, Oliver Rader a
a Helmholtz-Zentrum Berlin für Materialien und Energie,, Hahn-Meitner-Platz, 1, Berlin, Germany
b Institut für Physik und Astronomie, Universitaet Potsdam
c Peter Grünberg Institut and Institute for Advanced Simulation
d Department of Physics, RWTH Aachen University, 52056 Aachen, Germany
e Institute of Energy and Climate Research, IEK-5 Photovoltaics, Forschungszentrum Jülich, 52425 Jülich, Germany
Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS23 & Sustainable Technology Forum València (STECH23) (MATSUS23)
#PhotoPero23 - Photophysics of halide perovskites and related materials – from bulk to nano
València, Spain, 2023 March 6th - 10th
Organizers: Sascha Feldmann, Maksym Kovalenko and Jovana Milic
Poster, Maryam Sajedi, 369
Publication date: 22nd December 2022

Both organic-inorganic and all-inorganic lead halide perovskites exhibit high energy-conversion efficiency, and defect tolerance, along with low charge carrier trapping, and low non-radiative recombination rates. Recently, many scientific groups have attributed such favorable electronic properties to phenomena such as Rashba and/or polaronic effects. In this work, we investigated the electronic band structure of two types of halide perovskites to verify these two generally accepted propositions.

A Rashba effect has been invoked to explain the high efficiency by prohibiting direct recombination. Particularly, in the valence band of MAPbBr3 a static Rashba effect was reported by angle-resolved photoemission and circular dichroism with giant values of 7 to 11 eVÅ. We present band dispersion measurements of MAPbBr3 and spin-resolved photoemission of CsPbBr3 to show that a large Rashba effect detectable by photoemission does not exist.

The formation of large polarons has also been proposed as the origin of excellent optoelectronic properties. Direct evidence for large-polaron formation was reported from a 50% effective mass enhancement in angle-resolved photoemission of topmost valence band of CsPbBr3 compared to the theoretically predicted mass. We present details of band dispersion measurements on CsPbBr3, combined with GW calculations to investigate the trace of large polarons. We argue that the effective mass can be explained solely on the basis of electron-electron correlation and large-polaron formation cannot be concluded from photoemission data.

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