Enhanced Exciton Diffusion in a CsPbBr3 Binary Nanocrystal Superlattice
Thomas Sheehan a, Taras Sekh b c, Maksym Kovalenko b c, William Tisdale a
a Massachusetts Institute of Technology (MIT), Department of Chemical Engineering, Green Bldg, Cambridge, MA 02142, EE. UU., Cambridge, United States
b Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg, 1, Zürich, Switzerland
c Laboratory for Thin Films and Photovoltaics, Empa Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Suiza, Dübendorf, Switzerland
Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS23 & Sustainable Technology Forum València (STECH23) (MATSUS23)
#PhotoPero23 - Photophysics of halide perovskites and related materials – from bulk to nano
València, Spain, 2023 March 6th - 10th
Organizers: Sascha Feldmann, Maksym Kovalenko and Jovana Milic
Poster, Thomas Sheehan, 323
Publication date: 22nd December 2022

Control of exciton transport is critical for the operation of quantum dot (QD) solids in optoelectronic devices. Exciton diffusion in perovskite QDs typically occurs through Förster resonant energy transfer, which depends on both the optical properties and spatial arrangement of the quantum dots. Recent synthetic advancements have allowed for more control over both these factors in binary nanocrystal superlattices (BNSLs). Additionally, the high degree of structural order in superlattices has the potential to result in coherent enhancements to exciton transport. Here, we use time-resolved photoluminescence microscopy to compare the exciton diffusivity as a function of temperature in a BNSL containing both 5.3 nm and 17.7 nm CsPbBr3 QDs, an ordered film of 17.7 nm CsPbBr3 QDs, and a disordered film of 5.3 nm CsPbBr3 QDs. We find that although photoluminescence from the BNSL is dominated by emission from the 17.7 nm QDs, the exciton diffusivity is higher in the BNSL than in the ordered 17.7 nm QDs at every temperature. Additionally, at cryogenic temperatures, the exciton diffusivity in the BNSL is about twice as large as the exciton diffusivity in either of the monodisperse samples. While this enhanced transport likely does not result from coherence, it is still a consequence of the higher structural order in the BNSL.

This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under award no. DE-SC0019345.

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