absorption intensity. This confirms that the quenching effect is
more significant in the case of 1:0.6. Here it is important to
mention that the
film thicknesses was kept constant (100
2
nm) in the case of all samples for PL and UV–vis studies. There is a
strong relationship between the photocurrent and PL intensity
[25]. The absorption of incident photon
flux in sensitizer of DSPS
would generate columbically bound electron-hole pairs (excitons).
These photo-generated excitons may either move back to the
ground state or dissociate at TiO2/sensitizer dyes, or at the
interface of bulk heterojunction of the two polymers, creating a
photocurrent in the external circuit.
Fig. 4(a) shows the photo current relationship of the DSPS and
stimulated illumination intensity. The graphs showed almost a
linear relationship between photo current and illumination
intensity. The increase in light intensity leads more molecules of
the sensitizer to be excited and results in the increased photo
current due to increase in the generation rate of mobile charge
carriers, consequently generating more I species in the DSPS. It
can be observed that the photo current in PCPDTBT:MEH-PPV
(1:0.6) is relatively high as compared to the other ratios, which
indicates that the optimum ratio of the PCPDTBT:MEH-PPV blend
can give rise to the pronounced magnitude of photo current. The
recombination of the charge carriers might be lower and optimum
phase separation might be attained in PCPDTBT:MEH-PPV (1:0.6)
volumetric ratio which may lead to higher photo current