Delayed-emission spectra films

A sample of PS-B photooxldlzed In DMM, repreclpltated and cast as a film, produced a delayed emission spectrum having a new phosphorescence band, 505 nm, with an excitation... 

Figure 2. The prompt fluorescence (dashed line) and delayed emission (solid line) of P2VN-Py films at 77K. The mole fraction of pyrene for the corresponding delayed emission spectrum is indicated on the figure. Note that the delayed emission spectrum was obtained with a more red-sensitive photomultiplier than the prompt emission (see Experimental section) (1).

Fig. 3.25 The absorption spectrum of a MeLPPP film at 80 K and delayed emission of a MeLPPP film at 80 K. The 0 4 delay between excitation with q 2.76 eVand detection was 5 ps. O Reprinted from [142], copyright 2002, with permission from the American Institute of 0 o Physics.

The inclusion of 5 wt% PCBM [l-(3-methoxycarbonyl)propyl-l-phe-nyl-[6,6]C6i] in the spin-coating solutions resulted in efficient polymer emission quenching for all the polythiophenes studied. The transient absorption spectra of the amorphous poly(541)/PCBM blend film. At 10 ps exhibited an absorption peak around 700 nm, similar to that observed for the poly(541) pristine film. The shape of the transient spectrum varied with time, with the absorption peak shifting from 700 nm at 10 is to 900 nm for time delays >100 (is, demonstrating the formation of two distinct transient species in the blend film. The monoexponential lifetime was t = 8 (is under Ar atmosphere and significantly shortened under 02 atmosphere. Monoexponential phase is therefore assigned to the decay of poly(541) triplet excitons. 

Finally, the presence of molecular aggregates in samples with complex morphology can play an important role in emission [111] because they can have large radiative rates and behave as energy sinks in the excited material [112]. As an example, Fig. 2.7 shows the AT/T spectra of an mLPPP film. The spectrum at short time delays (0.4 ps) exhibits singlet S features PB at 450 nm, SE at 500 nm and PA at 840 nm. These decay on the 100 ps time scale. The spectrum at 400 ps shows absorption bands assigned to charged... 

Figure 8 is the phosphorescence spectrum taken from a glassy solution of poly(n-propyl methyl silylene) in methyl cyclopentane at 89°K. This emission is similar in width to the film emission, as are the solution spectra of the other polymers. Again delayed fluorescence is evident but the sharp vibrational fine structure is lost. The solution and film spectra are not expected to be comparable since they represent conformational equilibria (at room temperature for film and the Tg of 3-methylpentane for the solutions). 

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.

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