The Role of Charge Carrier Localization in the Phase Segregation of MAPb(I1-xBrx)3
Klara Suchan a, Justus Just b, Pascal Becker c, Carolin Rehermann c, Aboma Merdasa c, Roland Mainz c, Ivan G. Scheblykin a, Eva L. Unger a c
a Chemical Physics and NanoLund, Lund University, PO Box 124, Lund, Sweden
b MAXIV Laboratory
c Helmholtz-Zentrum Berlin for Materials and Energy
Proceedings of nanoGe Fall Meeting 2021 (NFM21)
#PerFun21. Perovskites I: Solar Cells, Lighting, and Related Optoelectronics
Online, Spain, 2021 October 18th - 22nd
Organizers: Eva Unger and Feng Gao
Poster, Klara Suchan, 293
Publication date: 23rd September 2021

The bandgap of mixed Br-I metal halide perovskites can be optimized for the application in tandem solar cells or LEDs by halide substitution. However, the photo-segregation, with its mechanistic origin still under debate, restricts the exploitation of the entire bandgap range. We investigate the full compositional range of MAPb(BrxI1-x)3 x = 0…1 by correlative simultaneous in-situ X-ray diffraction and photoluminescence spectroscopy during illumination. The complementary nature of both measurement techniques allows to describe the compositional redistribution upon illumination as well as its kinetics quantitatively and consistently for all sample compositions and compare these to the evolution of the luminescent states. We find that Br-rich samples exhibit a stronger final degree of segregation as well as faster segregation kinetics visible in XRD. We rationalize this asymmetric behaviour based on the difference in bandgap between newly formed utmost I-rich domains and the bandgap of the bulk material.

E. L. U. and K. S. acknowledge financial support from the Swedish Research Council (grants no. 2015-00163 and 2019-05014) and Marie Sklodowska Curie Actions, Cofund, Project INCA 600398 and Nano Lund. E. L. U., A. M. and C. R. also like to acknowledge financial support from the German Federal Ministry of Education and Research (BMBF–NanoMatFutur Project HyPerFORME: 03XP0091). C. R. acknowledges financial support from the HI-SCORE research school of the Helmholtz Association. The work was also supported by the Swedish Research Council grant no. 2016-04433. 

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