Quantum efficiency and photovol talc §~ ~roperties of a photodiode made of ;/ poly (3-4(-octylphenyl)-2, 2'-bithiophene) (ptopt)
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Date
2000-10
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Addis Ababa University
Abstract
In this thesis we investigated the photovoltaic properties of poly [3-(4-
octylphenyl)-2, 2'-bithiophene] (PTOPT) in the form of AI/PTOPT/ITO sandwich
structure. The peaks of the spectral response of the device were found to match
with the absorption spectrum of PTOPT for illumination from both the AI and ITO
sides. However, the IPCE% obtained when the device was illuminated from the AI
side is found to be lower than for illumination from the ITO side. The experimentally
collected data on absorption and action spectrum are explained based on the
theoretical model proposed by Gosh and Feng. The photovoltaic parameters were
determined from the I-V curve recorded by illuminating the photodiode through the
AI side with monochromatic light (500 nm) of intensity 7.4 JlW/cm2. No correction
was done for reflection from the surface of the AI electrode. A power conversion
efficiency of 0.7% and a fill factor of 0.25 were also obtained. The small value of
the efficiency is due to the low mobility of the charge carriers of the photodiode.
Moreover, the short circuit photocurrent of the device was found to vary with the
incident light intensity. The observed variation of the photocurrent with the incident
light irradiation (linear at low light intensities and non-linear at higher light
intensities) will be explained using a simple kinetic model
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Investigated the Photovoltaic Properties