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  • Real-Time Observation of Exciton-Phonon Coupling Dynamics in Self-Assembled Hybrid Perovskite Quantum Wells.

Real-Time Observation of Exciton-Phonon Coupling Dynamics in Self-Assembled Hybrid Perovskite Quantum Wells.

ACS nano (2017-10-25)
Limeng Ni, Uyen Huynh, Alexandre Cheminal, Tudor H Thomas, Ravichandran Shivanna, Ture F Hinrichsen, Shahab Ahmad, Aditya Sadhanala, Akshay Rao
ABSTRACT

Self-assembled hybrid perovskite quantum wells have attracted attention due to their tunable emission properties, ease of fabrication, and device integration. However, the dynamics of excitons in these materials, especially how they couple to phonons, remains an open question. Here, we investigate two widely used materials, namely, butylammonium lead iodide (CH3(CH2)3NH3)2PbI4 and hexylammonium lead iodide (CH3(CH2)5NH3)2PbI4, both of which exhibit broad photoluminescence tails at room temperature. We performed femtosecond vibrational spectroscopy to obtain a real-time picture of the exciton-phonon interaction and directly identified the vibrational modes that couple to excitons. We show that the choice of the organic cation controls which vibrational modes the exciton couples to. In butylammonium lead iodide, excitons dominantly couple to a 100 cm-1 phonon mode, whereas in hexylammonium lead iodide, excitons interact with phonons with frequencies of 88 and 137 cm-1. Using the determined optical phonon energies, we analyzed photoluminescence broadening mechanisms. At low temperatures (<100 K), the broadening is due to acoustic phonon scattering, whereas at high temperatures, LO phonon-exciton coupling is the dominant mechanism. Our results help explain the broad photoluminescence line shape observed in hybrid perovskite quantum wells and provide insights into the mechanism of exciton-phonon coupling in these materials.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Butane-1,4-diammonium iodide
Sigma-Aldrich
Hexane-1,6-diammonium iodide
Sigma-Aldrich
Di-iso-Propylammonium iodide
Sigma-Aldrich
n-Hexylammonium iodide
Sigma-Aldrich
n-Dodecylammonium iodide
Sigma-Aldrich
N,N-Dimethylpropane-1,3-diammonium iodide
Sigma-Aldrich
n-Octylammonium iodide, Greatcell Solar®
Sigma-Aldrich
2- Methyloxyethylammonium iodide
Sigma-Aldrich
Di-n-Propylammonium iodide