DOI: https://doi.org/10.29363/nanoge.inform.2019.051
Publication date: 8th January 2019
Two-dimensional hybrid lead halide perovskite derivatives have garnered considerable interest for opto-electronic applications, due to the presence of strongly bound and stable excitons even at room temperature. While the excitons in these systems seem to be analogous to those in semiconductor quantum wells, polar lattice fluctuations and dynamic disorder give rise to strong exciton-phonon coupling effects. We have recently identified clear signatures of polaronic effects on the excitonic correlations via quantitative analysis of linear and non-linear optical spectral[1][2]. Here, we establish that the dynamic structural complexity in a prototypical 2D lead iodide perovskite results in the coexistance of diverse exciton resonances, each with distict degree of polaronic character. We coherently excite and probe vibrational wavepacket dynamics by means of high resolution impulsive stimulated Raman spectroscopy, that evolve along different configurational coordinates defined by the normal vibrational modes of the lattice. Based on density functional theory calculations, we assign the observed vibrational modes to various low-frequency (< 50 cm-1) optical phonons involving the motion within the lead iodide layer. We demonstrate that different excitons induce specific lattice reorganizations, which are signatures of their polaronic binding.
A.R.S.K. acknowledges funding from EU Horizon 2020 via a Marie Sklodowska Curie Fellowship (Global) (Project no. 705874).
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