Analysis of photocurrent spectra at polybithienyl film coated on Pt |
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| Authors: | W F Zhang P Schmidt-Zhang G Koßmehl |
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| Institution: | Institut für Organische Chemie, Freie Universit?t Berlin, Takustrasse 3, D-14195 Berlin, Germany, DE
Forschungszentrum Sensorik Greifswald eV, Brandteichstrasse 19, D-17489 Greifswald, Germany, DE
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| Abstract: | Photoelectrochemical measurements have been performed at a polybithienyl (PBT) film (doping level of 1 × 1018/cm3) deposited on a platinum electrode. The cathodic photocurrents and negative slope of the Mott-Schottky plot indicate that
the PBT film has the features of a p-type semiconductor. The cathodic photocurrents are interpreted in terms of the Gaertner-Butler
model on the basis of the theory of the semiconductor|solution interface. The (i
ph
hν)2/n vs. hν plots taken from the photocurrent spectra show two linearities for n=1 in the wavelength range from 460 nm to 490 nm and for n=4 in the wavelength range λ > 490 nm. The band gaps of the PBT film were determined to be 2.05 ± 0.05 eV for n=1 and 1.55 ± 0.05 eV for n=4. The flat-band potential is 0.33 V (vs SCE). From the slope of the Mott-Schottky plot at the modulation frequency of 3 kHz,
the dielectric constant ɛ of the film and the thickness of the depletion layer W
0 of the PBT film were determined to be 7.4 and 0.29 μm, respectively.
Received: 6 January 1999 / Accepted: 6 June 1999 |
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| Keywords: | Polybithienyl Organic semiconductor Photocurrent Gaertner-Butler model Band gap energy |
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