Brennan Michael C, Forde Aaron, Zhukovskyi Maksym, Baublis Andrew J, Morozov Yurii V, Zhang Shubin, Zhang Zhuoming, Kilin Dmitri S, Kuno Masaru
Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States.
International Doctoral Program in Science, Università Cattolica del Sacro Cuore, Via Musei 41, 25121 Brescia, Italy.
J Phys Chem Lett. 2020 Jul 2;11(13):4937-4944. doi: 10.1021/acs.jpclett.0c01407. Epub 2020 Jun 10.
Size-dependent photoluminescence Stokes shifts (Δ) universally exist in CsPbX (X = Cl, Br, or I) perovskite nanocrystals (NCs). Δ values, which range from ∼15 to 100 meV for NCs with average edge lengths () from approximately 13 to 3 nm, are halide-dependent such that Δ(CsPbI) > Δ(CsPbBr) ≳ Δ(CsPbCl). Observed size-dependent Stokes shifts are not artifacts of ensemble size distributions as demonstrated through measurements of single CsPbBr NC Stokes shifts (⟨Δ⟩ = 42 ± 5 meV), which are in near quantitative agreement with associated ensemble ( = 6.8 ± 0.8 nm) Δ values (Δ ≈ 50 meV). Transient differential absorption measurements additionally illustrate no significant spectral dynamics on the picosecond time scale that would contribute to Δ. This excludes polaron formation as being responsible for Δ. Altogether, the results point to an origin for Δ, intrinsic to the size-dependent electronic properties of individual perovskite NCs.
尺寸依赖的光致发光斯托克斯位移（Δ）普遍存在于CsPbX（X = Cl、Br或I）钙钛矿纳米晶体（NCs）中。对于平均边长（）约为13至3 nm的NCs，Δ值范围为约15至100 meV，其与卤化物有关，使得Δ（CsPbI）>Δ（CsPbBr）≳Δ（CsPbCl）。通过测量单个CsPbBr NC的斯托克斯位移（⟨Δ⟩ = 42±5 meV）表明，观察到的尺寸依赖的斯托克斯位移不是整体尺寸分布的假象，其与相关整体（ = 6.8±0.8 nm）的Δ值（Δ≈50 meV）几乎定量一致。瞬态差分吸收测量还表明，在皮秒时间尺度上没有显著的光谱动力学对Δ有贡献。这排除了极化子形成是导致Δ的原因。总之，结果指向了Δ的起源，这是单个钙钛矿NCs尺寸依赖的电子特性所固有的。
