320
J Fluoresc (2010) 20:315–320
The quantum yield of our bifluorophore was determined
References
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measurement of the integral of luminescence curves I and
absorption coefficients on the same wavelength for un-
known and reference media. Then the quantum yield 8 is
determined according to:
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ꢀ ꢁꢀ
ꢁ
2
ꢇ
ꢈ
I
n
"
r
8 ¼ 8r
ð5Þ
Ir
nr
"
where n, I, 8, ε are the respective refraction coefficient,
integral intensity of luminescence, quantum yield and
absorbance of studied solutions, and nr, Ir, 8r, εr are the
same quantities of reference medium. As the reference
medium we select 2,5-Diphenyloxazole (РРО) solution in
cyclohexane with quantum yield 8r–0.99 [16]. Measurement
shows that the bifluorophore quantum yield is 8 =0.47.
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Conclusions
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Synthesized bifluorophore consists of pyrene molecules as
the donor and naphtylamide molecules as the acceptor of
excitation energy. It is shown in the paper that the resulting
absorption spectrum of the bifluorophore is the sum of
donor and acceptor respective spectra. So the total
absorption is increased allowing to utilize more wide part
of the Sun spectrum in a luminescent concentrator (LSC).
Donor emission in a 380–450 nm band (UF—blue) almost
disappears in the bifluorophore being shifted to green-red
band about 500–600 nm. This in turn allows more effective
coupling with the organic photovoltaic cell.
Quantum yield of obtained bifluorophore is rather low
now, about 0.47 and is increasing is the subject of further
investigations.
It is shown in the present work that observed effective
radiationless energy transfer cannot be explained by
Förster’s theory. It can be relate with small distance
between the donor and the acceptor in the bifluorophore.
This problem requires more detailed separate study.
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