Universal Size-Dependent Stokes Shifts in Lead Halide Perovskite Nanocrystals
Universal Size-Dependent Stokes Shifts in Lead Halide Perovskite Nanocrystals
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DOI：
10.1021/acs.jpclett.0c01407
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发表时间：
2020-07-02
影响因子：
5.7
通讯作者：
Kuno, Masaru
中科院分区：
文献类型：
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作者：
Brennan, Michael C.;Forde, Aaron;Kuno, Masaru
CsPbX_3（X = Cl-，Br-，I-）钙钛矿纳米晶普遍存在尺寸依赖的光致发光斯托克斯位移（Δ E-s）。对于平均边长（I）为约13至3 nm的NC，Δ E-s值的范围为类似于15至100 meV，其是卤化物依赖性的，使得Δ E-s（CsPbI 3）> Δ E-s（CsPbBr 3），大于或类似于Δ E-s（CsPbCl 3）。所观察到的尺寸依赖性斯托克斯位移不是系综尺寸分布的伪影，如通过测量单个CsPbBr 3 NC斯托克斯位移（= 42 +/-5 meV）所证明的，其与相关系综（1 = 6.8 +/-0.8 nm）AE值（Δ E-s近似于（）50 meV）接近定量一致。瞬态差分吸收测量另外说明在皮秒时间尺度上没有显著的光谱动态，这将有助于Δ E-s。这排除了极化子的形成是Δ E-s的原因。总而言之，结果指向Delta E-s的起源，这是单个钙钛矿NC的尺寸依赖性电子特性所固有的。
Size-dependent photoluminescence Stokes shifts (Delta E-s) universally exist in CsPbX3 (X = Cl-, Br-, or I-) perovskite nanocrystals (NCs). Delta E-s values, which range from similar to 15 to 100 meV for NCs with average edge lengths (l) from approximately 13 to 3 nm, are halide-dependent such that Delta E-s(CsPbI3) > Delta E-s(CsPbBr3) greater than or similar to Delta E-s(CsPbCl3). Observed size-dependent Stokes shifts are not artifacts of ensemble size distributions as demonstrated through measurements of single CsPbBr3 NC Stokes shifts ( = 42 +/- 5 meV), which are in near quantitative agreement with associated ensemble (l= 6.8 +/- 0.8 nm) AE, values (Delta E-s approximate to( )50 meV). Transient differential absorption measurements additionally illustrate no significant spectral dynamics on the picosecond time scale that would contribute to Delta E-s. This excludes polaron formation as being responsible for Delta E-s. Altogether, the results point to an origin for Delta E-s, intrinsic to the size-dependent electronic properties of individual perovskite NCs.