Abstract:
This work reports a study of the effects of Cadmium Sulfide (CdS) interlayer on the performance of
the Nanoporous Titanium dioxide (TiO2)/Poly (3-hexylthiophene)(P3HT) solar cells. CdSnano layers
with different thicknesses were successfully grown on TiO2 nanoparticles by chemical bath deposition
(CBD) technique with different deposition times. UV– Vis–NIR spectroscopic and Atomic Force
Microscopic measurements were taken for studying optical and structural properties of Titanium
dioxide (TiO2)/Poly (3-hexylthiophene)(P3HT) nanocomposite film with varying CdS interlayer
thicknesses while current-voltage (I–V) and external quantum efficiency (EQE) measurements were
done for evaluating the corresponding devices. Overall efficiency is optimized when the CdS
deposition time is 12 minutes which is consistent with AFM images as the images confirm the
uniform distribution of chemical bath deposited CdS layer on porous TiO2 until deposition time is 12
minutes. Roughness of CdS film decreased when the deposition time of CdS is increased further. The
short-circuit current density (JSC) and hence overall efficiency is declined when the CdS deposition
time is more than 12 minutes. The increment of CdS deposition time showed a gradual decrement in
the EQE spectra at 520 nm due to the lower polymer intake due to the CdS filled pores in TiO2
electrode as confirmed by the AFM images.The reduction in the JSC may also be attributed to lowering
interfacial area. On the other hand, a steady and continuous increment in the open circuit voltage
(VOC) were also observed with increased CdS deposition time and increased up to 0.81 V when the
CdS layer deposition time was 24 minutes. This may attribute to the isolation of P3HT and TiO2
interfaces and the higher built-in voltage at CdS – P3HT interface when to compare with TiO2 –
P3HT interface. An optimized CdS coated porous TiO2/P3HT solar cell shows the overall efficiency
of over 2.4 % under the illumination of 70 mW/cm2
at A.M 1.5 conditions.
