ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The photoinduced generation and the transport of charge carriers have been investigated in sandwich structures of Langmuir–Blogdett films of phthalocyaninato-polysiloxane between aluminum and gold electrodes. The diodelike current–voltage characteristics as well as the photovoltaic properties are directly related to the asymmetric electrode configuration. Under short-circuit conditions the photoactive region is located close to the aluminum electrode. By applying an external bias, the photoactive region is enlarged throughout the whole film thickness, and collection efficiencies of up to 0.3% are observed. Recombination effects have been studied by investigating the intensity dependence of the photocurrent. Nearly square root behavior under short circuit conditions is due to efficient charge carrier recombination whereas a linear intensity dependence is observed under reverse bias, indicating charge carrier diffusion to the electrodes. The transition between these two regimes is analyzed with respect to the charge carrier mobility yielding a value as small as 10−11 cm2/V s. The anisotrope molecular orientation in the film causes a photoconductivity clearly depending on the polarization of the incident light. The formation of a microcavity in these structures strongly influences the spectral properties and it allows, in agreement with theoretical calculations, to obtain an improved efficiency in a selected region of low film absorption. Atmospheric oxygen doping results in clear increase in the dark current, but the charge generation process remains nearly unaffected. © 1998 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.368551
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