Colloidal Cu⁺-doped CdSe/CdS core/shell semiconductor nanocrystals (NCs) are investigated in their as-prepared and degenerately n-doped forms using time-resolved photoluminescence and transient-absorption spectroscopies. Photoluminescence from Cu⁺:CdSe/CdS NCs is dominated by recombination of delocalized conduction-band (CB) electrons with copper-localized holes. In addition to prominent bleaching of the first excitonic absorption feature, transient-absorption measurements show bleaching of the sub-bandgap copper-to-CB charge-transfer (ML_CBCT) absorption band and also reveal a photoinduced midgap valence-band (VB)-to-copper charge-transfer (L_VBMCT) absorption band that extends into the near-infrared, as predicted by recent computations. The photoluminescence of these NCs is substantially diminished upon introduction of excess CB electrons via photodoping. Time-resolved photoluminescence measurements reveal that the ML_CBCT excited state is still formed upon photoexcitation of the n-doped Cu⁺:CdSe/CdS NCs, but its luminescence is quenched by a fast (picosecond) three-carrier trap-assisted Auger recombination process involving two CB electrons and one copper-bound hole.

中文翻译：

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掺杂铜的CdSe / CdS纳米晶体的光掺杂和瞬态光谱

使用时间分辨的光致发光和瞬态吸收光谱学研究了胶态Cu ⁺掺杂的CdSe / CdS核/壳半导体纳米晶体（NCs）的制备形式和简并的n掺杂形式。Cu ⁺：CdSe / CdS NCs的光致发光主要由离域导带（CB）电子与铜局部空穴的复合引起。除了第一个激子吸收特征的显着漂白之外，瞬态吸收测量还显示了亚带隙铜到CB电荷转移（ML _CB CT）吸收带的漂白，并且还揭示了光致中带价带（VB）到铜的电荷转移（L _VB如最近的计算所预测的那样，MCT吸收带延伸到近红外。这些NC的光致发光在引入过量CB电子的显着减少通过光掺杂。时间分辨的光致发光测量表明，在对n掺杂的Cu ⁺：CdSe / CdS NCs进行光激发时，仍会形成ML _CB CT激发态，但是通过快速（皮秒）三载流子陷阱辅助的俄歇复合体来猝灭其发光。此过程涉及两个CB电子和一个铜束缚空穴。