Behavior of Methylammonium Dipoles in MAPbX(3) (X = Br and I)

Autor(en)

Sharada Govinda, Bhushan P. Kore, Menno Bokdam, Pratibha Mahale, Abhinav Kumar, Somnath Pal, Biswajit Bhattacharyya, Jonathan Lahnsteiner, Georg Kresse, Cesare Franchini, Anshu Pandey, D. D. Sarma

Abstrakt

Dielectric constants of MAPbX

₃ (X = Br, I) in the 1 kHz-1 MHz range show strong temperature dependence near room temperature, in contrast to the nearly temperature-independent dielectric constant of CsPbBr

₃. This strong temperature dependence for MAPbX

₃ in the tetragonal phase is attributed to the MA

⁺ dipoles rotating freely within the probing time scale. This interpretation is supported by ab initio molecular dynamics simulations on MAPbI

₃ that establish these dipoles as randomly oriented with a rotational relaxation time scale of ∼7 ps at 300 K. Further, we probe the intriguing possibility of transient polarization of these dipoles following a photoexcitation process with important consequences on the photovoltaic efficiency, using a photoexcitation pump and second harmonic generation efficiency as a probe with delay times spanning 100 fs-1.8 ns. The absence of a second harmonic signal at any delay time rules out the possibility of any transient ferroelectric state under photoexcitation.

Organisation(en)

Computergestützte Materialphysik

Externe Organisation(en)

Indian Institute of Science

Journal

The Journal of Physical Chemistry Letters

Band

8

Seiten

4113-4121

Anzahl der Seiten

9

ISSN

1948-7185

DOI

https://doi.org/10.1021/acs.jpclett.7b01740

Publikationsdatum

09-2017

Peer-reviewed

Ja

ÖFOS 2012

103025 Quantenmechanik, 103036 Theoretische Physik, 103015 Kondensierte Materie, 103009 Festkörperphysik

Schlagwörter

ASJC Scopus Sachgebiete

Allgemeine Materialwissenschaften, Physical and Theoretical Chemistry

Sustainable Development Goals

SDG 7 – Bezahlbare und saubere Energie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/0d633fe1-6825-474a-a82a-c9e479d194f0