Department of Physics, University of Oxford , Clarendon Laboratory, Parks Road, Oxford OX1 3PU, U.K.
Nano Lett. 2013 Sep 11;13(9):4280-7. doi: 10.1021/nl402050q. Epub 2013 Aug 12.
We have investigated the dynamics of hot charge carriers in InP nanowire ensembles containing a range of densities of zinc-blende inclusions along the otherwise wurtzite nanowires. From time-dependent photoluminescence spectra, we extract the temperature of the charge carriers as a function of time after nonresonant excitation. We find that charge-carrier temperature initially decreases rapidly with time in accordance with efficient heat transfer to lattice vibrations. However, cooling rates are subsequently slowed and are significantly lower for nanowires containing a higher density of stacking faults. We conclude that the transfer of charges across the type II interface is followed by release of additional energy to the lattice, which raises the phonon bath temperature above equilibrium and impedes the carrier cooling occurring through interaction with such phonons. These results demonstrate that type II heterointerfaces in semiconductor nanowires can sustain a hot charge-carrier distribution over an extended time period. In photovoltaic applications, such heterointerfaces may hence both reduce recombination rates and limit energy losses by allowing hot-carrier harvesting.
我们研究了含有不同密度闪锌矿包的磷化铟纳米线组件中热载流子的动力学，这些纳米线在其他方面都是纤锌矿型的。通过时间分辨光致发光光谱，我们提取了非共振激发后载流子随时间的温度。我们发现，载流子温度最初随时间迅速下降，符合热向晶格振动的有效传递。然而，随后冷却速率变慢，在含有更高密度堆垛层错的纳米线中，冷却速率显著降低。我们得出结论，在 II 型界面处的电荷转移之后，会向晶格释放额外的能量，这会使声子浴的温度高于平衡温度，并阻碍通过与这些声子相互作用而发生的载流子冷却。这些结果表明，半导体纳米线中的 II 型异质结可以在较长时间内维持热载流子分布。在光伏应用中，这种异质结可以通过热载流子收集来降低复合速率并限制能量损失。
