Electrospun
ZnO Nanowire Plantations in the Electron Transport Layer for High-Efficiency
Inverted Organic Solar Cells
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Abstract
Inverted bulk heterojunction organic
solar cells having device structure ITO/ZnO/poly(3-hexylthiophene)
(P3HT):[6,6]-phenyl C61 butyric acid methyl ester (PCBM) /MoO<sub>3</sub>/Ag were fabricated with high photoelectric conversion efficiency
and stability. Three types of devices were developed with varying
electron transporting layer (ETL) ZnO architecture. The ETL in the
first type was a sol–gel-derived particulate film of ZnO, which
in the second and third type contained additional ZnO nanowires of
varying concentrations. The length of the ZnO nanowires, which were
developed by the electrospinning technique, extended up to the bulk
of the photoactive layer in the device. The devices those employed
a higher loading of ZnO nanowires showed 20% higher photoelectric
conversion efficiency (PCE), which mainly resulted from an enhancement
in its fill factor (FF). Charge transport characteristic of the device
were studied by transient photovoltage decay and charge extraction
by linearly increasing voltage techniques. Results show that higher
PCE and FF in the devices employed ZnO nanowire plantations resulted
from improved charge collection efficiency and reduced recombination
rate