Affiliation:
1. Faculty of Engineering Physics and Nanotechnology, VNU-University of Engineering and Technology, Vietnam National University, 144, Xuanthuy, Caugiay, Hanoi, Vietnam
Abstract
Background:
The active layer not only must have a strong light absorption in the visible
spectrum but must also be sufficient for charge carrier transport to the electrodes. Electrons in conducting
polymer transport by hopping between different energy levels resulted in much lower charge
mobility. Therefore, the thickness of the active layer must be limited, so the separated charge can
reach the corresponding electrodes without recombination. However, a thin active layer has weaker
light absorption, resulting in the low photogenerated current in organic solar cell devices. Furthermore,
buffer layers usually have high charge mobility, which in turn would enhance the transportation
of charge from the active layer to electrodes. Metal oxides have been studied to be used as a
cathode buffer layer, such as titanium dioxide (TiO2), zinc oxide (ZnO), etc.
Objective:
In this work, behaviors of the photon-electrical characteristics with variation in thickness
of the active (poly(3-hexylthiophene-2,5-diyl) and phenyl-C61 butyric acid methyl ester blend) and
buffer (zinc oxide) layers were investigated.
Methods:
The influences of the thickness of the active and buffer layers on characteristic parameters
of organic solar cells were investigated by solving the drift and diffusion equation with the photogenerated
current given by the Hetch equation.
Results:
The optimum thickness was obtained around 100 nm and below 10 nm for the active and the
ZnO buffer layers, respectively.
Conclusion:
Thinner active layer resulted in lower photocurrent due to poor light absorption while at
150 nm thick and above, PCE of the device reduced rapidly because of the high recombination rate
of photogenerated electron-hole pairs. ZnO buffer layer was used as an electron transport layer and a
hole blocking layer in order to improve the cell’s performance. The addition of ZnO enhanced the
PCE up to 2.48 times higher than the conventional device.
Publisher
Bentham Science Publishers Ltd.
Subject
Pharmaceutical Science,Biomedical Engineering,Medicine (miscellaneous),Bioengineering,Biotechnology