In this work, we investigated the effect of
single walled carbon nanotubes (SWCNT) on the electrical
and photovoltaic properties of methyl red (MR) dye based
photoelectrochemical cell (PEC). MR dye based PEC with
LiClO 4 as ion salt were fabricated with and without mixing
SWCNT. The cells were characterized through electrical
and optical measurements. The performance of the devices
changed drastically in presence of SWCNT. The transition
voltage and trap energy of the cells were estimated from
the steady-state dark current voltage (I-V) analysis. The
transition voltage and trap energy decreased for MR dye
cell in presence of SWCNT. Open circuit voltage (V oc ),
short circuit current (J sc ), fill factor (FF) and power
conversion efficiency (η) increased due to the addition of
SWCNT. Further measurement of the transient photo-
current showed that the growth and decay of photocurrent
was quite faster in presence of SWCNT. The photocurrent
decay with time was fitted for both the cells and found to
follow a power law relation which indicates dispersive
transport mechanism with exponential trap states distrib-
uted in between lowest unoccupied molecular orbital
(LUMO) and highest occupied molecular orbital (HOMO)
levels. Possible interpretation is done on the lowering of
trap energy with the photocurrent. These results suggest
that SWCNT lowers the trap energy of the cells by
providing efficient percolation pathways for the conduc-
tion of charges. It is expected that due to lowering of trap
energy the residing time of the free carriers within the traps
decreases. In other words, it may also be said that the
charge recombination decreases. These factors affect the
overall conduction of charges and improve the electrical
and photovoltaic properties.

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• Improvement of electrical and photovoltaic properties of methyl red dye based photoelectrochemical cells in presence of single walled carbon nanotubes