Preparation of Multi-Wall Carbon Nanotubes/Graphene Composites with Cadmium Sulfide in Dye-Sensitized Solar Cells (DSSCs)

In the present work, Dye Sensitized Solar Cells (DSSCs) have been fabricated by utilizing a dense layer of photoelctrode cadmium sulfide thin film (CdS) as n-type, which prepared by spray coating, while p-type electrode was mul-ti-wall carbon nanotubes/graphene (MWNT-G) composites. The experimen-tal results showed the higher energy conversion efficiency for CdS/MWNT-G was 0.056% in comparison with the others, which were CdS/MWNT with 0.044% and CdS/G with 0.037% respectively, which referred to improvement in the conductivity by using MWNT-G. The microstructure and nanostructure of CdS, MWNT, G, and MWNT-G nanocomposite were carried out by employing Scanning Electron Microscopy (SEM). X-Ray Diffraction (XRD) has been used to get crystal size of CdS, Raman scattering, and optical absorption also used for characterizations the samples. This study promised to increase and enhance the conversion efficiency of photovoltaic devices.


Introduction
Dye-sensitized photoelectrodes lie at the root of many recent developments used to advance processes central to photovoltaic, photocatalytic, and optoelectronic instruments [1] [2] [3]. These photoelectrodes pair a semiconductor film that has an inherently wide band gap, with a dye. As the name suggests, the dye plays a significant part in the charge transfer and light absorption characteristics of How to cite this paper: Alkuam, E. (2021) Preparation of Multi-Wall Carbon Nanotubes/Graphene Composites with Cadmium Sulfide in Dye-Sensitized Solar Cells 1.
Metallic sulfides [4] and chalcogenide compounds [5] have been a long-term focus for researchers who study photocatalysis, over several recent decades.
Cadmium sulfide (CdS) is one semiconductor photocatalyst that has attracted continuous investigation because two of its important characteristics are optimal: the fitting location of the conduction band and valence band edge, alongside the useful band gap of the compound [4] [6] [7].
Because of their capability to transport high current and their mechanical flexibility, multi-walled carbon nanotubes (MWNTs) have demonstrated marked benefits in the role of conducting matrix in nanocomposites [22].

Solar Cell Fabrication
The

Characterization
Scanning Electron Microscopy (SEM, JEOL JSM7000F) was used to investigate the microstructure and nanostructure of the samples. Raman spectra were analyzed by EZRaman-N to get more information about the crystalline of the film. UV-visible spectrometer was employed to measure the optical absorbance. The crystal structure of the synthesized CdS was determined by X-ray diffractometer (XRD) patterns on a Rigaku Miniflex 600 X-ray diffractometer with copper target; the wavelength of Copper K-alpha Cu Kα radiation is 1.54056 Å. Keithley 2400 sourcemeter measuring was employed to record current-voltage (I-V) characteristics.     (112) plane respectively referring that film is hexagonal CdS phase.

Results and Discussion
From Scherer formula [23] 0.94 cos D = λ β θ , where D is the crystallite size, λ the wavelength of the X-ray radiation (Cu Kα = 0.15406 nm), θ the diffraction angle and β is the full width at half maximum (FWHM) of the peak, particle size of CdS for H (002) before and after annealing was calculated and it was 49 ± 0.9 nm and 71 ± 7 nm before and after annealing respectively, it can be observed that the intensity and sharpness peak corresponding to the plane (002) increases after the annealing, which in terms indicate to improve the crystal size of CdS after annealing. Advances in Materials Physics and Chemistry Two optical vibrational Raman modes for CdS can be observed at 300 cm −1 and 600 cm −1 , as shown in Figure 5(b). In nanometer sized, the strong and sharper Raman peak of CdS shifted to a wavenumber 300 cm −1 referred to fundamental longitudinal optical phonon (1LO) while the broadband peak at wavenumber 600 cm −1 indicates to the first overtone mode (2LO), it is reasonable with the reports [24]. Figure 6 shows the typical absorption spectra of FTO, CdS with and without dye. It is notable that the absorbance of the CdS with dye is higher than that of the CdS only and absorbs more photons in the region between 420 -900 nm, which shows that the incident light harvested by a dye molecules.

Conclusion
MWNT, G, and MWNT-G nanocomposite film were successfully prepared by spray coating deposition on FTO, which employed as counter electrode to fabricate DSSCs with photo electrode n-CdS. The properties of the thin film were analyzed and characterized by different techniques. An improvement in power conversion energy was observed when MWNT-G nanocomposite used in the photovoltaic device, which is attributed to large surface coverage of MWNT-G and increased the conductivity, while the lowest power conversion energy might be attributed to the poor dye regeneration.