Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
Nano Lett. 2011 Mar 9;11(3):1136-40. doi: 10.1021/nl104054t. Epub 2011 Feb 2.
Biexciton properties strongly affect the usability of a light emitter in quantum photon sources and lasers but are difficult to measure for single fluorophores at room temperature due to luminescence intermittency and bleaching at the high excitation fluences usually required. Here, we observe the biexciton (BX) to exciton (X) to ground photoluminescence cascade of single colloidal semiconductor nanocrystals (NCs) under weak excitation in a g((2)) photon correlation measurement and show that the normalized amplitude of the cascade feature is equal to the ratio of the BX to X fluorescence quantum yields. This imposes a limit on the attainable depth of photon antibunching and provides a robust means to study single emitter biexciton physics. In NC samples, we show that the BX quantum yield is considerably inhomogeneous, consistent with the defect sensitivity expected of the Auger nonradiative recombination mechanism. The method can be extended to study X,BX spectral and polarization correlations.
双激子特性强烈影响量子光子源和激光中的发射器的可用性，但由于在通常需要的高激发通量下发光的间歇性和漂白，难以在室温下测量单个荧光团的双激子特性。在这里，我们在 g((2))光子相关测量中观察到单个胶体半导体纳米晶体（NC）在弱激发下的双激子（BX）到激子（X）到基态光致发光级联，并表明级联特征的归一化幅度等于 BX 与 X 荧光量子产率的比值。这对可实现的光子反聚束的深度施加了限制，并为研究单发射器双激子物理提供了一种稳健的手段。在 NC 样品中，我们表明 BX 量子产率存在相当大的不均匀性，这与预期的俄歇非辐射复合机制的缺陷敏感性一致。该方法可以扩展到研究 X、BX 的光谱和偏振相关性。
