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Recombination dynamics in CdTe/CdSe type-II quantum dots

机译：CdTe / CdSe II型量子点中的重组动力学

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摘要

Recombination dynamics in CdTe/CdSe core-shell type-II quantum dots (QDs) has been investigated by time-resolved photoluminescence (PL) spectroscopy. A very long PL decay time of several hundred nanoseconds has been found at low temperature, which can be rationalized by the spatially separated electrons and holes occurring in a type-II heterostructure. For the temperature dependence of the radiative lifetime, the linewidth and the peak energy of PL spectra show that the recombination of carriers is dominated by delocalized excitons at temperatures below 150 K, while the mixture of delocalized excitons, electrons and holes overwhelms the process at higher temperature. The binding energy of delocalized excitons obtained from the temperature dependence of the non-radiative lifetime is consistent with the theoretical value. The energy dependence of lifetime measurements reveals a third power relationship between the radiative lifetime and the radius of QDs, the light of which can be shed by the quantum confinement effect. In addition, the radiative decay rate is found to be proportional to the square root of excitation power, arising from the change of wavefunction overlap of electrons and holes due to the band bending effect, which is an inherent character of a type-II band alignment.
机译：通过时间分辨光致发光（PL）光谱研究了CdTe / CdSe II型核壳量子点（QDs）中的重组动力学。在低温下发现非常长的PL衰减时间为数百纳秒，这可以通过在II型异质结构中发生空间上分离的电子和空穴来合理化。对于辐射寿命的温度依赖性，PL谱的线宽和峰值能量表明，在150 K以下的温度下，载流子的重组以离域激子为主，而在更高温度下，离域激子，电子和空穴的混合物使该过程不堪重负温度。由非辐射寿命的温度依赖性获得的离域激子的结合能与理论值一致。寿命量度的能量依赖性揭示了辐射寿命与量子点半径之间的三次幂关系，量子约束效应可以揭示量子点半径。此外，发现辐射衰减率与激发能的平方根成正比，这是由于带弯曲效应引起的电子和空穴的波函数重叠变化而引起的，这是II型带取向的固有特征。 。

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