Size-dependent electronic decays and coherent phonon of CdSeTe quantum dots in glass matrix

•Our signal noise ratio of single color pump–probe measurement is bigger than 105.•Obvious coherent phonon of CdSeTe QDs (R = 3.9 nm) in glass matrix was observed.•Coherent phonon is attributed to resonant excitation because of Fröhlich coupling.•The component with long lifetime (~ ns) under non-resonant excitation originated from heat accumulation.

The ultrafast decays of CdSexTe1 − x (x = 0.32) quantum dots in the glass matrix were reported by use of one-color pump probe experiments. The size varies from 7.8 to 22 nm, has a longer rising time and a much longer lifetime. Obvious coherent phonons and electronic decays of CdSexTe1 − x quantum dots (R = 3.9 nm) are found with the excitation of band-edge energy, but only long electronic decays of CdSexTe1 − x quantum dots (R = 5.3, 11.0 nm) are observed. Coherent phonon is attributed to resonant excitation because of Fröhlich coupling. The component with long lifetime under non-resonant excitation originated from heat accumulation.