Colloidal CdSe quantum dots (QDs) designed with a high degree of asymmetric internal strain have recently been shown to host a number of desirable optical properties including subthermal room-temperature line widths, suppressed spectral diffusion, and high photoluminescence (PL) quantum yields. It remains an open question, however, whether they are well-suited for applications requiring emission of identical single photons. Here we measure the low-temperature PL dynamics and the polarization-resolved fluorescence line narrowing spectra from ensembles of these strained QDs. Our spectroscopy reveals the radiative recombination rates of bright and dark excitons, the relaxation rate between the two, and the energy spectra of the quantized acoustic phonons in the QDs that can contribute to relaxation processes. In comparison to conventional colloidal CdSe/ZnS core/shell QDs, we find that in asymmetrically strained CdSe QDs over six times more light is emitted directly by the bright exciton. These results are therefore encouraging for the prospects of chemically synthesized colloidal QDs as emitters of single indistinguishable photons.

中文翻译：

---

不对称应变胶体 CdSe/CdxZn1-xSe 量子点中亮激子的增强发射

设计有高度不对称内部应变的胶体 CdSe 量子点 (QD) 最近已被证明具有许多理想的光学特性，包括亚热室温线宽、抑制光谱扩散和高光致发光 (PL) 量子产率。然而，它们是否非常适合需要发射相同单光子的应用仍然是一个悬而未决的问题。在这里，我们测量低温 PL 动力学和来自这些应变 QD 集合的偏振分辨荧光线变窄光谱。我们的光谱揭示了亮暗激子的辐射复合率、两者之间的弛豫率，以及量子点中可能有助于弛豫过程的量子化声子的能谱。与传统的胶体 CdSe/ZnS 核/壳量子点相比，我们发现在不对称应变的 CdSe 量子点中，亮激子直接发射的光超过六倍。因此，这些结果对于化学合成胶体量子点作为单个不可区分光子的发射体的前景是令人鼓舞的。