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Insights on Anisotropic Emission of (Diffused) Photo-Carriers in Hybrid Perovskite Microrods
Journal
Journal of Physical Chemistry C
ISSN
19327447
Date Issued
2022-09-22
Author(s)
Behera, Tejmani
Chowdhury, Arindam
Abstract
Quasi one-dimensional (1D) semiconductor materials with inherent anisotropic emission have numerous advantages in terms of brightness, color enhancement, and efficiency for optoelectronics and light-emitting devices. Herein, we report the anisotropic optical absorption and emission of individual methyl-ammonium lead bromide (MAPbBr3) microrods (MRs). We find that the absorption and emission polarization direction is along the long axis of the MRs, and the degree of polarization (DOP) remains unaltered with the excitation field orientation as well as with the modulation in excitation energy. Polarization-resolved emission spectroscopy of individual MRs reveals that the orthogonally polarized fluorescence emissions originate from equivalent energy states, in contrast to other semiconductors rods. To explore the polarized PL emission behavior of the diffused photo-excited charge carriers, we employed an optical setup where MRs are locally excited at a confocal spot, and emission is imaged over the entire rod. Although photo-excited carriers in perovskites are known to have short initial polarization memory, we observe anisotropic emission far away, beyond several hundred nanometers from the excitation spot. This is remarkable and indicates strongly polarized radiative recombination of photogenerated carriers which migrate along the long axis of the crystals. Our measurements on single MRs in different dielectric media reveal that the electric field renormalization inside the crystal owing to dielectric changes at the interface is primarily responsible for such observed anisotropy in optical behaviors. The employed imaging method can potentially be used to explore the anisotropic emission behavior of photo-excited and diffused photo-carriers in various other semiconductor microcrystals with different material compositions, where excitation energy is transferred over long distances.