Proceedings of nanoGe Fall Meeting 2021 (NFM21)
DOI: https://doi.org/10.29363/nanoge.nfm.2021.166
Publication date: 23rd September 2021
Many nanostructured materials when observed in a fluorescence microscope demonstrate fluctuations of local photoluminescence intensity. The fluctuations vary from drastic ON/OFF blinking of individual semiconductor nanocrystals to rather mild PL intensity flickering of micrometre-sized grains in metal halide perovskite films. The following necessary conditions for this phenomenon to occur can be formulated:
1) the material must contain some very strong metastable PL quenching sites (or efficient non-radiative (NR) recombination centres sometimes called super traps[1]) which switch from their active to passive state at the time scale of the experiment,
2) just one such NR centre should be able to substantially decrease PL quantum yield of the whole region over which photogenerated excitations (electrons, holes, excitons) can diffuse,[2,3]
3) these regions must be isolated from each other in such a way that luminescence microscope resolves them.
Luminescence micro-spectroscopy is an ideal tool study local PL intensity fluctuations and correlate them with local PL spectroscopic properties with spatial resolution limited by light diffraction. Moreover, naturally fluctuating PL allows for application of super-resolution methods based on PL blinking to increase the spatial resolution of imaging and local spectroscopy.[1] In addition activation/de-activation of a super trap in a nanocrystal drastically changes the local energy relaxation pathways and can reveal local energy inhomogeneities via PL spectral fluctuations couples with fluctuations of PL intensity.[4]
In my lecture I will illustrate the general ideas described above on MAPbI3 perovskite semiconductor where a very pronounced PL blinking effect allows for studying of local photophysics and photochemistry of this semiconductor.[5]
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