Photocarrier recombination dynamics in ternary chalcogenide CuInS2 quantum dots.
Photocarrier recombination dynamics in ternary chalcogenide CuInS2 quantum dots (CIS QDs) was studied by means of femtosecond transient-absorption (TA) and nanosecond time-resolved photoluminescence (PL) spectroscopy. Under strong excitation, the TA dynamics in CIS QDs is well described by a simple rate equation including single-carrier trapping, free-to-bound recombination, and trap-assisted Auger recombination. Under weak excitation, on the other hand, the PL decays of the QDs are composed of a short-lived component caused by surface trapping and a long-lived one caused by free-to-bound recombination. It is found that the surface trapping accelerates markedly with decreasing QD size while the free-to-bound radiative recombination hardly depends on the QD size. Besides this, we observed both a decrease in the PL lifetimes and a dynamic spectral redshift, which are attributed to the surface trapping and the coexistent inhomogeneous broadening in CIS QDs. The spectral redshift becomes less pronounced in CIS/ZnS core/shell QDs because of the suppression of the fast nonradiative recombination caused by the passivation of the surface traps. These results give clear evidence that the free-to-bound model is appropriate for interpreting the optical properties of CIS QDs.
State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China. zhaojl@ciomp.ac.cn.
Jianhui
J
Sun
Michio
M
Ikezawa
Xiuying
X
Wang
Pengtao
P
Jing
Haibo
H
Li
Jialong
J
Zhao
Yasuaki
Y
Masumoto