Time-resolved photoluminescence spectra

Fig. 2.48 Time-resolved photoluminescence spectra of PFB F8BT blends of different weight ratios, (a), (b) and (c), and of films of pure PFB and F8BT (d). The spectrum with the highest intensity represents the PL emission integrated over the first 10 ns. The less-intense spectra are the delayed PL integrated over subsequent 10-ns time windows, i.e. over 10-20 ns, 20-30 ns,..., 80-90 ns.

Earlier, the lifetime of charge carriers in GaAs superlattices was determined from the time-resolved photoluminescence spectra [3]. Changes in the total and radiative lifetimes were analyzed in the model with no k-selection rule and possible broadening effects. In spite of this, the predictions agree qualitatively with the observed increasing of the lifetime within the red shift of the decaying luminescence spectra. 

Figure 13.9 Time-resolved photoluminescence spectra, detected at various emission wavelengths. The decay curves are the same for all wavelengths.

Time-resolved photoluminescence was also used to show that the spatial separation of the electron and hole wavefunctions due to the piezoelectric fields in GalnN/GaN QWs leads to a dramatic reduction in oscillator strength, particularly for thick quantum wells [6]. Due to the reduced oscillator strength for the lowest energy state, the optical absorption spectrum of the quantum wells is expected to be dominated by highly excited states close to the strained bulk bandgap. 

Figure 7.5 Ultrafast spectrally resolved dynamics of two CdS tSei x nanobelts. The fluorescence image is shown in the upper left corner. Note that the broad, time-integrated photoluminescence spectrum shown on the left consists of two distinct features centered at 628 and 636 nm with vastly different dynamics that is clearly discernible in the 2D map.

FIGURE 12.14 Shown are the absorption and photoluminescence from Ru(dcb)(bpy)2/Ti02 immersed in acetonitrile. The addition of LiC104 to the acetonitrile resulted in a red shift in the absorption spectrum (shown by dotted line) and aquenching of the photoluminescence intensity that was shown to result from oxidative quenching by the conduction band. Time-resolved data were most consistent with the model shown Li+ adsorption to Ti02 promotes rapid excited-state injection. 

Figures 8.4 and 8.5 show the luminescence spectrum and the time-resolved emission decay of MEH-PPV/ Cgo composites compared with MEH-PPV alone. The strong photoluminescence of MEH-PPV is quenched by a factor in excess of 10, and the luminescence decay time is reduced from 7o 550 picoseconds to Trad 60 picoseconds (the instrumental resolution) indicating the existence of a rapid quenching process [53,54, 63]. An estimate of the transfer rate, l/td, is given by decay rate of the photoluminescence in the MEH-PPV/Cgo composite (charge transfer will cut off the radiative decay).

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