AI Article Synopsis
- - The Stokes shift in two-dimensional (2D) CsPbBr perovskites is significant, changing from 26 to 41 meV with temperature, unlike in bulk perovskites where it is negligible.
- - The differences in absorption and photoluminescence (PL) peaks are attributed to the exciton fine structure, where multiple bright excitons are involved in absorption but only the lowest level emits light.
- - The observed characteristics, including PL decay and the splitting of excitons, are related to the unique anisotropic morphology of the 2D perovskite structure, suggesting that a large Stokes shift is an inherent trait of these materials.
Article Abstract
The Stokes shift is negligible in bulk perovskites but large in two-dimensional (2D) CsPbBr perovskites. The issue has attracted a lot of discussion, but it remains controversial. Here, we report the temperature-dependent absorption and photoluminescence (PL) spectra of CsPbBr perovskite nanoplatelets (NPLs). We observe a temperature-dependent Stokes shift changing from 26 to 41 meV. This phenomenon was attributed to the exciton fine structure according to the great difference in peak width. The triple bright exciton levels all participate in the absorption process and result in a wide absorption peak, while only the lowest exciton level contributes to photon emission and exhibits a relatively narrow PL peak. The PL decay curves also present the characterization of bright and dark exciton couplings at low temperatures. The splitting of triple bright excitons is induced by the morphology anisotropy of the 2D structure, so the large Stokes shift is proposed to be an intrinsic property of 2D perovskites.
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| http://dx.doi.org/10.1021/acs.jpclett.3c01641 | DOI Listing |
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