Inversion symmetry and bulk Rashba effect in methylammonium lead iodide perovskite single crystals
Methylammonium lead iodide perovskite (MAPbI_3) exhibits long charge carrier lifetimes that are linked to its high efficiency in solar cells. Yet, the mechanisms governing these unusual carrier dynamics are not completely understood. A leading hypothesis—disproved in this work—is that a large, static bulk Rashba effect slows down carrier recombination. Here, using second harmonic generation rotational anisotropy measurements on MAPbI_3 crystals, we demonstrate that the bulk structure of tetragonal MAPbI_3 is centrosymmetric with I4/mcmspace group. Our calculations show that a significant Rashba splitting in the bandstructure requires a non-centrosymmetric lead iodide framework, and that incorrect structural relaxations are responsible for the previously predicted large Rashba effect. The small Rashba splitting allows us to compute effective masses in excellent agreement with experiment. Our findings rule out the presence of a large static Rashba effect in bulk MAPbI_3, and our measurements find no evidence of dynamic Rashba effects.
© 2018 The Author(s). This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Received: 01 December 2017; Accepted: 12 April 2018; Published: 08 May 2018. M.B. acknowledges partial support from start-up funds and from the Space Solar Program Initiative at the California Institute of Technology. K.F. thanks the California Institute of Technology for support through the SURF fellowship program, and Peter Foley and Linn Leppert for fruitful discussions. SHG-RA measurements were supported by the U. S. Department of Energy under grant DE-SC0010533. D.H. also acknowledges funding for instrumentation from the Institute for Quantum Information and Matter, an NSF Physics Frontiers Center (PHY-1125565) with support of the Gordon and Betty Moore Foundation through grant GBMF1250. O.M.B and W.P. acknowledge the support of KAUST. J.B.N. and S.G.L. were supported by the U.S. Department of Energy, Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, under Contract No. DE-AC02-05CH11231, through the Theory FWP (KC2301) at Lawrence Berkeley National Laboratory (LBNL). This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02- 05CH11231. Data availability: The authors declare that the data supporting the findings of this study are available within the paper and its Supplementary Information files. Author Contributions: M.B. conceived the project. K.F. and M.B. carried out the calculations and prepared the manuscript with input from co-authors. W.P. and O.B. synthesized and provided the samples. T.D., J.H., and D.H. designed and conducted the experiments. B.B. contributed to the calculations. J.B.N. and S.G.L. contributed to conceive the theory and calculations. All authors edited the manuscript. The authors declare no competing interests.
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