Photophysics of Two-Dimensional Perovskites—Learning from Metal Halide Substitution


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Abstract

Whereas their photophysics exhibits an intricate interplay of carriers with the lattice, most reports have so far relied on single compound studies. With the exception of variations of the organic spacer cations, the effect of constituent substitution on the photophysics and the nature of emitting species, in particular, has remained largely under-explored. Here PEA2PbBr4, PEA2PbI4, and PEA2SnI4 are studied through a variety of optical spectroscopy techniques to reveal a complex set of excitonic transitions at low temperature. We attribute the emergence of weak high energy features to a vibronic progression breaking Kasha's rule and highlight that the responsible phonons cannot be accessed through simple Raman spectroscopy. Bright peaks at lower energy are due to two distinct excitons, of which the upper is a convolution of a bright exciton and a localised state, whereas the lower is attributed to shallow defects. Our study offers deeper insights into the photophysics of two-dimensional perovskites through compositional substitution and highlights critical limits to the communities' current understanding of the photophysics of these compounds.

Description
Keywords
2D perovskites, defects, excitons, magneto-photoluminescence, photophysics, Ruddlesden-Popper phases
Journal Title
Advanced Functional Materials
Conference Name
Journal ISSN
1616-301X
1616-3028
Volume Title
31
Publisher
Wiley
Sponsorship
Deutsche Forschungsgemeinschaft (408012143)
Dutch Research Council (739.017.005)