Time-resolved photoinduced absorption spectroscopic study on trapped carriers at semiconductor-glass interfaces

The photoinduced absorption below the band gap of a color glass filter doped by CdS_0.4Se_0.6 microcrystals was investigated by using time-resolved differential transmittance spectroscopy. The electron trapping at microcrystal-glass interfaces was found to occur within less than 1 ps after photoexcitation. At low excitation energy density, the excited electrons are trapped at point detects distributed over the nanocrystal interfaces. Such electrons give rise to long-lived photoinduced absorption with a lifetime of 3.2 ns. On the other hand, at high excitation energy density, transient absorption with a fast (60 ps) and simultaneously a slow decay component (3.2 ns) was observed. This short-lived photoinduced absorption is attributed to the electrons trapped at the shallow trap states of the semiconductor-glass interfaces.