School of Physics and Astronomy & Photon Science Institute, University of Manchester, Manchester, M13 9PL, UK.
Phys Chem Chem Phys. 2012 Nov 21;14(43):15166-72. doi: 10.1039/c2cp42125a. Epub 2012 Sep 11.
Colloidal nanocrystal quantum dots with a band gap in the near infra-red have potential application as the emitters for telecommunications or in vivo imaging, or as the photo-absorbing species in next generation solar cells or photodetectors. However, electro- and photoluminescence yields and the efficiency with which photo-generated charges can be extracted from quantum dots depend on the total rate of recombination, which can be dominated by surface-mediated processes. In this study, we use ultrafast transient absorption spectroscopy to characterise the recombination dynamics of photo-generated charges in InAs/ZnSe nanocrystal quantum dots. We find that recombination is dominated by rapid, sub-nanosecond transfer of conduction band electrons to surface states. For the size of dots studied, we also find no evidence of significant multiple exciton generation for photon energies up to 3.2 times the band gap, in agreement with our theoretical modelling.
具有近红外带隙的胶体纳晶量子点在电信或体内成像的发射器，或在下一代太阳能电池或光电探测器中作为光吸收物质方面具有潜在应用。然而，电致发光和光致发光产率以及可以从量子点中提取光生电荷的效率取决于总复合速率，而总复合速率可能由表面介导的过程主导。在这项研究中，我们使用超快瞬态吸收光谱来描述 InAs/ZnSe 纳晶量子点中光生电荷的复合动力学。我们发现，复合主要是通过导带电子快速（亚纳秒级）转移到表面态来进行的。对于我们所研究的量子点的大小，我们也没有发现对于光子能量高达带隙的 3.2 倍的情况下存在显著的多激子产生的证据，这与我们的理论模型一致。
