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Charge Carriers Are Not Affected by the Relatively Slow-Rotating Methylammonium Cations in Lead Halide Perovskite Thin Films.

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Caselli, Valentina M 
Fischer, Mathias 
Meggiolaro, Daniele  ORCID logo
Mosconi, Edoardo 
De Angelis, Filippo  ORCID logo


Recently, several studies have investigated dielectric properties as a possible origin of the exceptional optoelectronic properties of metal halide perovskites (MHPs). In this study we investigated the temperature-dependent dielectric behavior of different MHP films at different frequencies. In the gigahertz regime, dielectric losses in methylammonium-based samples are dominated by the rotational dynamics of the organic cation. Upon increasing the temperature from 160 to 300 K, the rotational relaxation time, τ, decreases from 400 (200) to 6 (1) ps for MAPb-I3 (-Br3). By contrast, we found negligible temperature-dependent variations in τ for a mixed cation/mixed halide FA0.85MA0.15Pb(I0.85Br0.15)3. From temperature-dependent time-resolved microwave conductance measurements we conclude that the dipolar reorientation of the MA cation does not affect charge carrier mobility and lifetime in MHPs. Therefore, charge carriers do not feel the relatively slow-moving MA cations, despite their great impact on the dielectric constants.



3403 Macromolecular and Materials Chemistry, 34 Chemical Sciences, 3406 Physical Chemistry

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J Phys Chem Lett

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American Chemical Society (ACS)
Royal Society (UF150033)