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

Abstract

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 photocurrent 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 distributed 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 conduction 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.

Correlation in Structural Architecture toward Fabrication of Schottky Device with a Series of Pyrazine Appended Coordination Polymers

“…The trap centers are expected to exponentially spread (eq ) the trapper charge density g false( E false) = N T k B T T exp true( − E n k T normalT true) is calculated from the total trap concentration ( N T ), Fermi energy ( E n ), Boltzmann constant ( k ), and characteristic temperature ( T T ). The I – V characteristic was evaluated (eq ) to obtain the power law, I ∼ V m +1 ; here, V = applied voltage and m = T T / T .…”

Effect of Single Walled Carbon Nanotubes on the Series Resistance and Trap Energy of Malachite Green Dye Based Organic Device

“…It can be seen that the flow of current increases significantly in presence of SWCNT. It can be said that the incorporation of SWCNT reduces the process of recombination by providing low percolation pathways for the charge carriers [12] which in turn results in improvement of the charge flow at the metal-organic layer interface.…”

“…The voltage across the device has been varied from 0 to 5 V in steps of 0.5 V with a delay of 1000 ms. The experiment has been performed in a normal room temperature of 26 0 C [12].…”

“…Due to the high trap energy, the charge carriers are trapped during the charge transport process and degrade the overall performance of the organic devices. Recently many works have been reported that with the incorporation of single walled carbon nanotubes (SWCNT) into the organic dyes the efficiency of the devices is increased [11][12]. Various promising properties such as good stability and flexibility, desirable optical properties, high carrier mobility, tunable conductivity, etc.…”

“…The aspect ratio of SWCNT is very high as the diameters of SWCNT are in the range of 0.4 to 2 nm and the length up to 1.5 cm [14]. This high aspect ratio SWCNT exhibit low percolation pathways which results in lowering of trap energy (Ec) and enhance the charge transport mechanism throughout the device [12]. This enhancement of the charge transport mechanism will increase the current which in turn reduces the Rs of the organic devices.…”