Hot Polarons with Trapped Excitons and Octahedra-Twist Phonons in CH3NH3PbBr3 Hybrid Perovskite Nanowires

TL;DR

This paper reveals that in CH3NH3PbBr3 nanowires, trapped excitons strongly interact with octahedra-twist phonons, forming hot polarons, which explains the defect tolerance and high efficiency in perovskite-based optoelectronic devices.

Contribution

It demonstrates the formation of hot polarons from trapped excitons interacting with transverse optical phonons in perovskite nanowires, highlighting a key physical mechanism behind their defect tolerance.

Findings

Observation of hot polarons with narrow linewidth in photoluminescence.

Confirmation of interaction via magneto-optical spectra showing Zeeman splitting.

Identification of octahedra-twist phonons as the primary interacting phonons.

Abstract

Hybrid Perovskites have shown a great potential for applications in photovoltaics and light-emitting devices with high efficiency. Interaction between defect-induced trapped excitons and phonons plays an important role in understanding the emerging phenomena for such an excellent figure-of-merit. Here we demonstrate hot polarons with narrow linewidth in $\mathrm{CH_{3}NH_{3}PbBr_{3}}$ nanowires, which originate from the interaction between trapped excitons and octahedra-twist phonons. The observation of hot polarons in photoluminescence without gain methods indicates the large interaction strength between excitons and phonons. The multiple hot polarons are further confirmed by magneto-optical spectra with a Zeeman splitting of the trapped excitons and a phonon energy increase with diamagnetic effect. Furthermore, the phonons participating in the interaction are demonstrated to be the octahedra-twist vibrations which are transverse optical phonons, while the interaction between trapped excitons and longitudinal optical phonons is weak. Our work demonstrates that trapped excitons in perovskites prefer to interact with transverse rather than longitudinal optical phonons. Since bulk materials usually interact with longitudinal optical phonons, this result provides a physical explanation of the high tolerance of defects in perovskites.