(543h) Understanding the Link of Photoluminescence Momentum and Lifetime in Perovskite Thin Films and Superlattices

We live in an incredibly exciting time. The observation of extraordinary quantum optical phenomena, which has been historically limited to very exotic materials, is now being observed in solution processed, colloidal nanomaterials such as perovskite nanocrystals (CsPbX3) [1], [2]. Because coherent and quantum phenomena exhibit highly directional properties that depend strongly on the timescales of various transitions and processes, we must understand the fundamental directional and time-dependent light-material properties of these perovskite nanocrystals in order to achieve these new technologies.

In this presentation, I will explore how surface effects and neighbor interactions drive the unique photophysical properties of CsPbBr3 nanocrystals using our newly developed technique: time-resolved back focal plane imaging. By using a photon counting fluorescence imaging camera that is combined with the optics of back focal plane (or Fourier) imaging [3], we can simultaneously image photoluminescence intensity and lifetime as a function of emitted photon angle (see Figure 1). This allows us to observe how the radiative rate varies across photon momentum. Here I will show data from monolayer films and superlattices assembled from colloidal cesium lead halide (CsPbX₃, X – halide) perovskite nanocrystals, which are known to have strong interactions with their local environments [4]. By comparing the monolayers to superlattices, we can understand how these rates and dipole interactions are changed between individual and collective states.

[1] G. Rainò, M. A. Becker, M. I. Bodnarchuk, R. F. Mahrt, M. V. Kovalenko, and T. Stöferle, “Superfluorescence from lead halide perovskite quantum dot superlattices,” Nature, vol. 563, no. 7733, pp. 671–675, 2018, doi: 10.1038/s41586-018-0683-0.

[2] B. Russ and C. N. Eisler, “The future of quantum technologies: superfluorescence from solution-processed, tunable materials,” Nanophotonics, Feb. 2024, doi: 10.1515/nanoph-2023-0919.

[3] J. A. Schuller et al., “Orientation of luminescent excitons in layered nanomaterials,” Nature Nanotechnology, vol. 8, no. 4, pp. 271–276, 2013, doi: 10.1038/nnano.2013.20.

[4] M. J. Jurow et al., “Manipulating the Transition Dipole Moment of CsPbBr 3 Perovskite Nanocrystals for Superior Optical Properties,” Nano Letters, vol. 19, no. 4, pp. 2489–2496, 2019, doi: 10.1021/acs.nanolett.9b00122.

Figure caption:

Figure 1. Left: Schematic of the back focal plane (BFP) imaging setup, the 3D emission pattern is projected onto the CCD camera. From left to right, calculated BFP images are shown for dipole alignments of 0° (parallel to substrate), 35.3°, and 90° (perpendicular to substrate). Right: Use of widefield photon counting fluorescence lifetime imaging camera to measure intensity and lifetime vs. angle.