Download High-pressure Affected Exciton Dynamics of CdSe/ZnS Core

High-pressure Affected Exciton Dynamics of CdSe/ZnS Core-shell Quantum
Dots
Ling-Yun PAN,a Yan LUO,a Zhi-Wei WANG,a Yong-Jun BAO,a Xiao-Li HUANG,a Qiang ZHOU,a
Dong-Xiao LU,a Tian CUI a*
a
College of Physics, State Key Laboratory Super Hard Materials, Jilin University, Changchun, Jilin, China
Because of the strong quantum confinement effect, the physical and chemical properties of
semiconductor quantum dots (QDs) shows great difference with bulk materials. The generated
exciton, electron-hole structure, can be seemed as the the hydrogen-like model which makes the
mechanism discussion much simple. Therefore, semiconductor QDs are good objects for fundamental
research in various fields. As a kind of condensed materials, their responses to extreme conditions,
such as high-pressure, are necessary to be investigated. Since high-pressure can precisely adjust the
spaces among QDs, the nearest-neighbor as well as long-range interaction can be modulated. As this
point of view, both individual and integrated performance, the high-pressure response physical
properties of QDs are very different from that of the bulk semiconductors.[1-3]
The high-pressure response of QDs mostly focused on the phase transition investigation,
which enable the research of transformation between stable states of finite system as comparing with
the infinite system for bulk materials. While, for semiconductor materials, the exciton dynamics is an
important process for both optical and electrical properties. Thus, high-pressure affected exciton
dynamics in QDs are worth to be investigated, in which may be helpful for new materials preparation,
such as materials for LEDs, detectors, photovoltaics, lasing media etc; or QDs’ application in extreme
environment, such as geological exploration etc.[4]
In this article, the exciton dynamics under high-pressures are observed in type-I core-shell
QDs by transient absorption method. In type-I QDs, shell serve as a tunneling barrier for the electron
and hole transfer. Exciton is confined inside the core and its diffusion is greatly reduced. Meanwhile,
the defects states are well modified by shell and trapping states correlated dynamics can be neglected.
Therefore, a relatively pure exciton dynamics can be observed in type-I QDs. The results show that
the multi-exciton interaction reduced very much as comparing with ambient condition. Both diffusion
and hopping time of excitons are extended. Coupling induced diffusion is the main dynamical process
for low pressure; while, tunneling induced hopping for high pressure.
References
[1]
Hu,T.; Isaacoff, B. P.; Bahng, J. H.; Hao, C. ;Zhou, Y. ;Zhu, J.; Li, X. ; Wang, Z. ;Liu, S.; Xu, C. ;Biteen,
J. S.; Kotov,N. A. Nano Lett. 2014, 14, 6799.
[2]
Sandeep, C.S.S. ; Ten Cate, S. ; Schins, J. M. ; Savenije, T. J. ; Liu, Y. ; Law, M. ; Kinge, S. ;Houtepen,
A. J. ; Siebbeles, L.D. A. Nature Commun. 2013, 4,2360.
[3]
Pan, L. Y.; Zhang, Y. L.; Wang, H. Y.; Liu, H.; Luo, J. S.; Xia, H.; Zhao, L.; Chen, Q. D.; Xu,
S. P.; Gao, B. R.; Fu, L. M.; Sun, H. B. Nanoscale, 2011, 3, 2822.
[4]
Jacobs, K., Alivisatos, A. P., Rev. Mineral. Geochem. 2001,44, 59.
* [email protected]
Keywords: High-pressure, Ultrafast spectroscopy, Exciton dynamics, Quantum dots.