Universal Size-Dependent Stokes Shifts in Lead Halide Perovskite Nanocrystals

Michael C Brennan; Aaron Forde; Maksym Zhukovskyi; Andrew J Baublis; Yurii V Morozov; Shubin Zhang; Zhuoming Zhang; Dmitri S Kilin; Masaru Kuno

doi:10.1021/acs.jpclett.0c01407

Universal Size-Dependent Stokes Shifts in Lead Halide Perovskite Nanocrystals

J Phys Chem Lett. 2020 Jul 2;11(13):4937-4944. doi: 10.1021/acs.jpclett.0c01407. Epub 2020 Jun 10.

Authors

Michael C Brennan^{1

2}, Aaron Forde³, Maksym Zhukovskyi⁴, Andrew J Baublis¹, Yurii V Morozov¹, Shubin Zhang⁵, Zhuoming Zhang¹, Dmitri S Kilin⁶, Masaru Kuno^{1

5}

Affiliations

¹ Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States.
² International Doctoral Program in Science, Università Cattolica del Sacro Cuore, Via Musei 41, 25121 Brescia, Italy.
³ Department of Materials and Nanotechnology, North Dakota State University, Fargo, North Dakota 58102, United States.
⁴ Notre Dame Integrated Imaging Facility, Notre Dame, Indiana 46556, United States.
⁵ Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556, United States.
⁶ Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102, United States.

PMID: 32482071
DOI: 10.1021/acs.jpclett.0c01407

Abstract

Size-dependent photoluminescence Stokes shifts (ΔE_s) universally exist in CsPbX₃ (X = Cl^-, Br^-, or I^-) perovskite nanocrystals (NCs). ΔE_s values, which range from ∼15 to 100 meV for NCs with average edge lengths (l) from approximately 13 to 3 nm, are halide-dependent such that ΔE_s(CsPbI₃) > ΔE_s(CsPbBr₃) ≳ ΔE_s(CsPbCl₃). Observed size-dependent Stokes shifts are not artifacts of ensemble size distributions as demonstrated through measurements of single CsPbBr₃ NC Stokes shifts (⟨ΔE_s⟩ = 42 ± 5 meV), which are in near quantitative agreement with associated ensemble (l = 6.8 ± 0.8 nm) ΔE_s values (ΔE_s ≈ 50 meV). Transient differential absorption measurements additionally illustrate no significant spectral dynamics on the picosecond time scale that would contribute to ΔE_s. This excludes polaron formation as being responsible for ΔE_s. Altogether, the results point to an origin for ΔE_s, intrinsic to the size-dependent electronic properties of individual perovskite NCs.