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In summary, the charge carrier photogeneration effi-ciency Z in solid films of PA-PPV and MEH-PPV has been

Summary: In summary, the charge carrier photogeneration effi-
ciency Z in solid films of PA-PPV and MEH-PPV has been
determined by xerographic discharge experiments over two
orders of magnitude in field and for different illumination
wavelengths. Onsager's theory with a Gaussian distribution
of electronħhole radii describes the electric field depen-
dences of Z well. The large distribution parameter a is a
characteristic of a small electronħhole pair binding energy
of approximately 0.1ħ0.2 eV. For both polymers, high effi-
ciencies of up to 20 % at a field of 100 V/mm were measured.
Within the polymer absorption, Z was found to be nearly in-
dependent of wavelength. This is in agreement with the well
established picture of a fast vibronic and energetic relaxa-
tion following photoexcitation. Addition of C60 to PA-PPV
increases the primary quantum yield to unity and photo-
generation efficiencies of up to 50 % are measured.
The investigated polymers were synthesized by polycondensation using
the principle of Horner, yielding polymers with well defined chemical struc-
ture [27ħ29]. Samples were prepared by spin-coating from toluene solution


Source: Ade, Harald W.- Department of Physics, North Carolina State University


Collections: Physics