Excitonic Spin-Coherence Lifetimes in CdSe Nanoplatelets Increase Significantly with Core/Shell Morphology
Excitonic Spin-Coherence Lifetimes in CdSe Nanoplatelets Increase Significantly with Core/Shell Morphology
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DOI：
10.1021/acs.nanolett.2c04845
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发表时间：
2023-02-08
期刊：
影响因子：
10.8
通讯作者：
Schaller，Richard D.
中科院分区：
文献类型：
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作者：
Martin，Phillip I.;Panuganti，Shobhana;Schaller，Richard D.
我们报道了胶体CdSe纳米片的自旋极化瞬时吸收是厚度(2-6单层厚度)和核/壳基序的函数。利用共偏振和交叉偏振泵浦-探测组合的电光调制，我们灵敏地观察到了自旋-偏振跃迁。只有核的纳米小片的自旋寿命只有几皮秒，但随层厚的增加而微弱增加。不同的自旋极化信号的光谱含量表明，双激子结合能随着厚度的增加而降低，并且比以前报道的值更小。具有可控厚度的Cd S的壳层生长，部分地使电子从空穴中离域，在室温下显著地增加了∼49ps的自旋寿命。硫化锌外壳的实现不会改变离域，但确实会改变表面终止，将自旋寿命延长到∼100ps，支持了这样的解释，即表面终止严重影响自旋相干，这可能是由于悬挂键的钝化。磁场中的自旋进动既证实了室温下长的相干寿命，又产生了激子因子。
We report spin-polarized transient absorption for colloidal CdSe nanoplatelets as functions of thickness (2–6 monolayer thickness) and core/shell motif. Using electro-optical modulation of co- and cross-polarization pump–probe combinations, we sensitively observe spin-polarized transitions. Core-only nanoplatelets exhibit few-picosecond spin lifetimes that weakly increase with layer thickness. The spectral content of differenced spin-polarized signals indicate biexciton binding energies that decrease with increasing thickness and smaller values than previously reported. Shell growth of CdS with controlled thicknesses, which partially delocalize the electron from the hole, significantly increases the spin lifetime to ∼49 ps at room temperature. Implementation of ZnS shells, which do not alter delocalization but do alter surface termination, increased spin lifetimes up to ∼100 ps, bolstering the interpretation that surface termination heavily influences spin coherence, likely due to passivation of dangling bonds. Spin precession in magnetic fields both confirms long coherence lifetime at room temperature and yields the excitonicgfactor.