Electrochemical Polymerization for Tyramide Derivative for Solar Cell Application

INTRODUCTION
A solar cell can be defined as a photovoltaic (PV) device which converts the energy of light to electrical energy. In particular, ETM (i.e., electron transport material) of a DSSC is made of a wide band gap semi-conductor that is deposited over a transparent conductive oxide (TCO) glass. The dye molecule is after that anchored to semiconductor surface as charge layer that can absorb visible light in dye region as well as transfer photo charges to hole- and electron- conducting materials. A redox-coupled electrolyte, usually consisting of iodide/triiodide ions (I− /I3 −), is known as the hole transport material (HTM). It contacts to a cathode or counter electrode (CE), in which oxidized donor reduction occurs. These days, the final PV efficiency of solar cells greatly depends on development of CEs for DSSCs. It is vital to identify alternative inexpensive and noble metal - free materials for replacing Pt in the DSSCs, and conducting polymers appear to have intriguing potential [2,3]. The first step is crucial in producing ionic conductivity (I-), which speeds up redox process and aids in the oxidized dye’s quicker rate of regeneration. Second, it is caging more cations, which raises the potential and causes the dye’s positive molecular orbital (HOMO) to shift downward [4]. This contributes to electron recombination rate reduction between holes in the dye’s HOMO and electrons in TiO2 conduction band. Moreover, pyridine is used as a donating material, which modifies TiO2 surface charge, shifting its conduction band upward and raising the open circuit voltage (Voc). The PV efficiency, which is defined as [5], is increased by this configuration by raising open circuit voltage (Voc). Fig. 1 illustrated DSSC principle [6–10]. Typically, excited state electrons inject semiconductor’s conduction band (CB) and then move across external circuit to counter electrode. In order to create reduced electrolyte and achieve electrolyte regeneration, oxidized electrolyte takes electrons from counter electrode; At interfaces of such three parts, electron recombination ions take place. In this regard, the three DSSC parts play essential and indispensable roles in determining how well the device performs. The selection and production of component materials are essential. The polymers could be utilized for fabricating flexible substrates, to create a mesoporous electrode structure, for preparing a polymer gel electrode, and catalyzing electrolyte reduction as counter electrodes.

MATERIALS AND METHODS
Preparation of electrolyte 
Gel- electrolyte was prepared by using Polyethylene glycol (PEG 4000) as high-molecular additive, KI as iodide, ACN as solvent, and I2 by molecular rate of 3.0g: 15.0ml: 2 gm: 0.2 gm [11].

Preparation of photo electrode (TiO2/Dye)
Through using the doctor blend method, TiO2 has been deposited on ITO glass with a resistance of 10Ω/cm2 and sintered for 30 mins at 450°C. Fig. 2 illustrates how the working electrode (TiO2 electrode) was immersed in eosin dye for 30 mins.

Preparation of poly counter electrode
Fig. 3 illustrates the electrochemical polymerization of Tyramide derivative (DE) onto the surface of Indium Tin oxide (ITO) in monomer solution by utilizing a DC power supply and two electrodes, the Country electrode (CE) and Working electrode (WE). Three drops of 95% H2SO4 were added to 100 milliliters of water together with 0.1 gram of Tyramide derivative as the solution used for electrochemical polymerization [12]. To improve the effectiveness of the polymer film, 0.004g of graphene was also added.

Structural and Morphological Measurements 
The Measurements include studying the structure and the surface morphological for the prepared films and the used materials by using FTIR, AFM, and SEM.

Fourier Transform Infrared Region Spectroscopy (FTIR)
FTIR is an instrument to determine organic functional group for liquid, powder, gases, and films by their structural groups. In this work this technique employed to characterize the synthesis polymer [13]. 

Atomic Force Microscope (AFM) 
The cantilever utilized for scanning the specimen surface for insulating surface structure at atomic resolution has a pointed tip, or probe, at the end. The attractive force between surface and the tip is sensed during scanning, which is a dynamic process because the tip is in mechanical contact with the specimen. The surface as well as tip’s Vander-Waals interaction generated such attractive force [14].

Scanning Electron Microscope (SEM)
The surface topography can be measured with electron beams with the use of SEM, an analytical instrument. The surface topography cannot be measured because the electron beam is concentrated from micro to nanometers through the magnetic field. Images of secondary electron (SE) or backscattered electron (BSE) modes are produced by SEM. Typically, SEM mode provided images based on topographical data [15].

X-Ray Diffraction (XRD)
XRD is the best method to determine the crystal structure and lattice parameters. The principle of XRD found in textbooks, such as the one by Buerger [16], Alexander and Klug [17], Cullity [139]. The studies of XRD considered the significant source to provide wide comprehension of the structure of a molecule and the crystal structure. The Bragg spectrometer principle for such study [18].

RESULTS AND DISCUSSION 
UV-Vis spectroscopy for Eosin dye 
The dye is used in this study is eosin dye, its chemical structure is shown in Fig. 4. The absorption spectrum of Eosin dye is exhibited in Figure. It is clear that it has absorption peaks at 523 nm,398 nm and 309 nm, which indicates that it has high transmission in these regions.

Mechanism of polymerization 
Characterization of poly Tyramide derivative film 
Fourier transmittance Infrared Region (FTIR)
Fig. 5 compares the FT-IR spectrum regarding the Tyramide derivative monomer as well as poly Tyramide derivative. FT-IR spectrophotometer (8400 max resolution 0.50cm-1) was used in order to perform the FTIR experiments for the prepared poly Tyramide derivative. The polymer film was proven to have formed when the aliphatic double bond (CH=CH) in the monomer’s spectra at 1616.24 cm-1 disappeared. Tyramide derivative monomer absorption band rates are shown in Table 1 [19]. 

Scanning Electron Microscope (SEM)
SEM was used to analyze surface morphological features of polymer film in both the presence and absence of graphene. SEM image for the polymer film, which revealed irregular distribution on the surface of S.S. with minimal porosity and compact structure, is displayed in Figs. 6a and 6b. Graphene modified polymer film, on the other hand, clearly showed particle size aggregation with a cluster poly structure on one side and a fiber-like poly structure on the other [20].

Atomic Force microscope (AFM) 
Since AFM is regarded as one of the notable surface examination tools for nanoscale structures, it was used to gather more information due to the significance of the nanomaterial’s surface qualities as well as their direct impact on efficiency through application. The 3D and 2D images in Figs. 7a, and 7b illustrate the extent of nanomaterial agglomeration caused by G’s adhesiveness to the polymer. The most often used metrics in AFM analysis for characterizing surface roughness for polymer films are average roughness (Ra) and root mean square roughness (RMS) [21, 22]. Table 2 provides a summary of the acquired Ra and RMS values. 

X-ray diffraction (XRD)
XRD for Graphene, poly Tyramide derivative and poly Tyramide derivative modified with Graphene are showed in Fig. 8. XRD for Graphene is showed in Fig. 8a involve broad peaks at (2ϴ = 25.07, 44.47 degree) [23]. Fig. 8b is showed XRD for poly Tyramide derivative film which involve sharp reflection peaks at (2ϴ=9.58,26.6 and 28.56 degree) and that reflect its crystallite nature. Fig. 8c is showed the effect of addition of Graphene in the polymer matrix. it is showed a broad peak at (2ϴ=26 degree). This peak reflected to interaction of Graphene sheets with polymer matrix.

Characterization of assembled DSSCs
DSSCs from mixed combination of different counter electrodes and different active anodes have been subjected to the I-V characterization by fast scan with two electrodes, potentiostate, to calculate all parameters of every one of them; current short circuit (Isc), voltage of open circuit (Voc), max cell power (Pmax=Im*Vm), have been estimated with the use of two electrodes potentiostatic measurements, then the full factor (FF),and conversion efficiency(E%) are calculated by the following equations[24]:

 I-V characteristic is measured by two types of electrodes, poly Tyramide derivative and poly Tyramide derivative modified with Graphene as shown in Fig. 9. Adding of Graphene to poly Tyramide derivative matrix improves the catalytic properties of poly Tyramide derivative. Table shows that DSSCs based on poly Tyramide derivative modified with graphene show higher efficiency than non-modified polymer. Since the high resistance of the poly Tyramide modified with Graphene would obstruct the electrons transport from external circuit to electrolyte, less reduction of I3 to I- is obtained [24]. All values of assemble DSSCs are listed in Table 3. 

CONCLUSION
In summary, the synthesized poly(tyramide derivative) film was successfully polymerized, as confirmed by the disappearance of the aliphatic C=CH stretch at 1616 cm-1 in FTIR spectra, alongside SEM revealing a compact morphology that evolves into clustered and fibrous structures upon graphene incorporation. AFM analysis demonstrated increased surface roughness due to graphene agglomeration, while XRD patterns exhibited crystalline peaks at 2θ = 9.58°, 26.6°, and 28.56° for the polymer, shifting to a broad interaction peak at ~26° with graphene, indicative of strong matrix-sheet interfacial bonding that boosts conductivity. The graphene-modified poly(tyramide derivative) counter electrode in DSSCs yielded higher short-circuit current (Isc), open-circuit voltage (Voc), fill factor (FF), and power conversion efficiency (η) compared to the unmodified polymer, attributed to improved catalytic reduction of I₃- to I- despite minor charge transport resistance, positioning this composite as a promising, cost-effective alternative for efficient dye-sensitized solar cells.

CONFLICT OF INTEREST
The authors declare that there is no conflict of interests regarding the publication of this manuscript.