Sensitizers Performance of Dye-Sensitized Solar Cells Fabricated With Indian Fruits and Leaves

Int. J. Adv. Sci. Eng. Vol. 1 No. 2 (2014) ISSN 2349 5359

K. M. Prabu, et al.,

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ABSTRACT: Hazardous chemicals escape into the environment due to many natural and manmade activities. They cause adverse effects on human health and environment. Natural dye-sensitized solar cells (NDSSCs) have gained considerable attention in the field of solar energy due to their simple fabrication, good efficiency, and low production cost. Natural dyes are environmentally and economically superior to ruthenium-based dyes, because they are nontoxic and cheaper. However, the conversion efficiency of dye-sensitized solar cells based on natural dyes is low. One way to improve the DSSC performance is to enhance the absorption (efficiency) of extracted natural dyes. The optical absorption and the functional group prepared from natural dyes were analyzed by using UV-Visible, PL-studies and FT-IR analysis. The optical absorption and surface morphology of pure and doped TiO2 Nanopaste coated on dye dipped FTO glass plate were analyzed by using UV-Visible and FE-SEM analysis. NDSSCs were assembled by using methanol treatment of Prunus Dulcis fruit, Red Indian Spin-ach leaves & Red Indian Spinach fruit dyes. Finally photo-voltaic characterizations of assembled nanocrystaline natural dye solar cells were analyzed by using J-V studies. The photo - electrochemical parameters, such as short-circuit current (Jsc), open-circuit voltage (Voc), fill factor (FF) and overall conversion efficiency (η) are evaluated.

Keywords: Pure and doped TiO2 photo-electrode, Prunus Dulcis fruit, Red Indian Spinach leaves & Red Indian Spinach fruit dyes.

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1. INTRODUCTION The conversion of solar radiation to electrical energy has become more and more important because sunlight is a clean and limitless energy source compared to the traditional fossil energy sources. Dye-sensitized solar cells (DSSCs) were first proposed by Gratzel in the early 1990's. They developed a DSSC with energy conversion efficiency exceeding 7% in 1991 and 11.4% in 2001 by combining nanostructure electrodes to efficient charge injection dyes. A DSSC is the third generation photovoltaic device for low cost conversion of solar energy into electrical energy. The

TiO2 has been widely studied for efficient DSSCs, and a power conversion efficiency of 11% was reported. Recent studies have shown that metal oxides such as ZnO, SnO2, Nb2O5- mainly TiO2, have been successfully used as photo-anode when a dye is absorbed in the interior of the porous layer [1-5]. The main features of natural dyes are their availability, evironmental friendly and cost effective. The efficiency of DSSCs with organic dyes was increased signifi-cantly in the last few years and the current state of the art (9 %) is comparable to the conventional Ru-complexes. Pure dye is extracted from Prunus Dulcis fruit, Red Indian Spinach leaves and Red Indian Spinach fruit by using various solvent such as methanol, ethanol and acetone.

INTERNATIONAL JOURNAL OF ADVANCED SCIENCE AND ENGINEERING

Journal Webpage : www.mahendrapublications.com

Received : 03.09.2014

Accepted : 24.10.2014

Sensitizers Performance of Dye-Sensitized Solar Cells Fabricated With Indian Fruits and Leaves

* Corresponding author

Phone : +91 9443659435

Email : [email protected] [email protected]

K. M. Prabu1, K. Suguna1, P. M. Anbarasan1,2, T. Selvankumar3, and

V. Aroulmoji4

1Department of Physics, Periyar University, Salem 636 011, Tamil Nadu, India 2Centre for Nanoscience & Nanotechnology, Periyar University,

Salem - 636 011, Tamil Nadu, India 3PG & Research Department of Biotechnology, Mahendra Arts and Science College,

Kalippatti, Namakkal-637 501, Tamil Nadu, India. 4Centre for Research and Development, Mahendra Educational Institutions,

Mallasamudram - 637 503, Tamil Nadu, India

24-32

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The optical absorption and functional group of prepared natural dyes were analyzed by using UV-Visible, PL-Studies and FT-IR analysis. Then the photo electrode was prepared by doctor-blade method from pure TiO2, Ag doped TiO2, Mg doped TiO2, Bi doped TiO2, Al doped TiO2 and ZnO doped TiO2 nanopaste. Next we investigate the optical absorption, surface morphology of dye dipped FTO glass plate by using UV-Visible, PL-studies and FE-SEM analysis. Finally photocurrent-voltaic characterizations of assembled nanocrystalline natural dye solar cells were analyzed by us-ing J-V studies also the levels of short-circuit current (Jsc), open-circuit voltage (Voc), fill factor (FF) and overall conver-sion efficiency (η) can be analyzed [6-14].

2. MATERIALS AND METHODS 2.1. Chemicals Used Most of the chemicals used in the research are standard chemicals that are normally available in the laboratory. Special materials for DSSC are mostly purchased from Solaronix. The chemicals used in this study were titanium tetrachloride, aluminum nitrate, bismuth nitrate, magnesium nitrate, zinc acetate dehydrate, benzyl alcohol, absolute ethanol, acetyl acetone, methanol, isopropanol, DFM solvent, Triton X-100, polyethylene glycol, Idolyte TG 50 and diethyl ether were purchased from Sigma-Aldrich. All the chemicals were used without further purification. 2.2. Sample Preparation Metal oxide nanoparticles attract great attention in recent years on account of their special electronic and chemical properties. In this paper, Al doped TiO2 nanoparticles with high photo catalytic activity were synthesized by sol-gel method. The nano TiO2 powder was prepared with titanium isopropoxide solution as the raw material. In a typical experiment, 0.05 mol % aluminium nitrate was dissolved in 60 ml of deionized water at room temperature, followed by adding 5 ml of glacial acetic acid to obtain solution A. 14 ml titanium isopropoxide was dissolved in 40 ml of anhydrous ethanol with constant stirring to form solution B. Then, the solution B was added drop-wise into the solution A within 2 hours under constant stirring. Subsequently, the obtained sol was stirred continuously for 3 h and kept for 3 days at room temperature. As-prepared TiO2 gels were dried for 10 h at 80°C. The obtained solids were ground and finally calcinated at 500°C for 2 h (heating rate = 5°C/min). This method has been followed by preparation of pure and Bi, Mg, Ag and ZnO doped TiO2 [15] 2.3. Substrate Cleaning Coated glass with highly F-doped Transparent Conducting Oxide (TCO) usually serves as a support for the dye-sensitized solar cell fabrication. It allows lightly transmission while providing good conductivity for current collection. The Substrates are first dipped into acetone in the ultrasonic bath for 20 minutes to dissolve the unwanted organic materials and to remove dust and contamination material that are left on the substrates post manufacture. Another 20 minutes of ultrasonic bath in methanol is

followed in order to remove the acetone and materials that are not cleansed or dissolved by acetone. Finally, a 30 minute ultrasonic bath in isopropanol was needed to further remove the residual particles on the substrates. 2.4. ZnO/TiO2 Photo - anode Deposition on FTO Glass Plate As it is very important to work with a fingerprint free F-doped TCO, gloves were used always and FTO was cleaned with alcohol prior to use. The FTO was heated to 50°C at the beginning of the process to increase the adhesion and the scotch 3M adhesive tapes were applied on the edge of the conductive side of the FTO glass plate. The reason for using tapes was to prepare a mould such that nano-sintered ZnO doped TiO2 has always same area and thickness for all samples. A certain proportion of ZnO doped TiO2 powder with ethanol, acetyl acetone; polyethylene glycol and triton (X-100) were mixed for 30 minutes in agate mortar. Then ZnO doped TiO2 colloidal was dropped on the conductive side of the FTO after the conductive side of the FTO was checked by the multimeter. Then, the ZnO doped TiO2 paste was uniformly distributed over the FTO by Doctor Blade method. Doctor Blade means a film smoothing method using any steel, rubber, plastic, or other type of blade used to apply or remove a liquid substance from another surface. The term “Doctor Blade” is derived from the name of a blade used in conjunction with the doctor roll on the letter press [16-17]. 2.5 Heat Treatment for Photo Anode The scotch 3M adhesive tapes were removed from the ZnO doped TiO2 coated FTO glass plate and plates were sintered at 450°C for 30 min in air. The colour of ZnO doped TiO2 becomes brown in the middle of the sintering process and then its colour changes to the brownish-white. This colour remained till the end of the sintering process. This is to ensure that the polymer or macromolecules in ZnO doped TiO2 colloid such as acetyl acetone can be removed, leaving tiny holes in nano layers, resulting in better dye absorption and better contact between ZnO doped TiO2 particles. In consequence, it optimizes the chances of electrons being excited by the photons and increases the amount of excited electrons entering into the ZnO doped TiO2 conduction band. 2.6. Preparation of Dye Sensitizer Solutions The Prunus Dulcis fruit, Red Indian Spinach leaves and Red Indian Spinach fruit were collected from Uthangarai Taluk, Krishnagiri District. Approximately 50 g of the sample was dissolved in 100 ml of methanol, ethanol and acetone. Then the pure solution was filtered out from solid residues by extraction process. Further purification of the extract was avoided to achieve efficient sensitization using simple extraction procedures. The extracts were properly stored, protected from sunlight and used further as photo sensitizers in DSSCs. 2.7. Preparation of Counter Electrode The platinization procedure given by Solaronix was applied because the material was taken from Solaronix

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Actually, this method is simply called thermal decomposition which is most widely used platinization procedure. Plastitol was applied on the surface by using a brush. All FTO glasses were sintered at 450°C for 15 minutes for decomposition which was the minimum required calcinations condition according to the procedure [18-19]. 2.8. Nano-crystalline Dye Sensitized Solar Cell Assembly Sensitized pure and doped TiO2 photo-anode and the counter electrode were stacked together face to face and the liquid electrolyte, Idolyte TG 50 solution drop penetrated into the working space and counter electrode via capillary action. The two electrodes were held with binder clips [18]. 3. RESULTS AND DISCUSSION 3.1 UV-Visible Absorption Spectroscopy Analysis The dye used as a photo - sensitizer plays an important role in the operation of DSSCs. The efficiency of the cell is critically dependent on the absorption spectrum of the dye and the anchorage of the dye to the surface of the semicon-ductor. The UV-Visible spectral studies of the Prunus Dul-cis fruit, Red Indian Spinach leaves and Red Indian Spinach fruit dyes were carried out by using Lambda 35 model UV-Visible spectrometer in the range of 200 to 1100 nm. The and Red Indian Spinach fruit dyes are extracted by using different medium such as methanol, ethanol and acetone corre-sponding to samples A, B, and C respectively as shown in fig-ures 3.1.1, 3.1.2 and 3.1.3. The UV-Visible spectra of Prunus Dulcis fruit dye shows the narrow light absorption in the range of 400 nm to 450 nm, Red Indian Spinach leaves dye shows the broad absorption peak at 200 nm to 300 nm in the UV region and sharp absorption peak at 300 nm to 450 nm in the visible region, Red Indian Spinach fruits dye shows the broad absorption peak at 200 nm to 350 nm in the UV region and high absorption with wider peak at 350 nm to 500 nm in the visible region. The methanol treatment of all the dyes exhibits the longer wavelength and broad light absorption in the visible region but the other solvents effect shows the smaller wavelength and narrow light absorption. A decrease in the intensity of absorption and wavelength range as we go from methanol to acetone is observed. So the dye extracted by using methanol solvent is found to be more effective compared to other solvents. The UV -Visible spectra of sample A obtains high absorbance, broader and longer wavelength while compared to other samples. These results concluded that the sample A belongs to the small band gap value compared to the other samples. The absorption spectrum of methanol solvent in all the dyes shows the entire visible region high absorption compared to other solvent medium. It is a good condition for solar cell applications. The UV-Visible absorption spectra of methanol solvent treated of Prunus Dulcis fruit, Red Indian Spinach leaves & Red Indian Spinach fruit dyes dipped FTO glass plate is shown figures 3.1.4, 3.1.5 & 3.1.6 respectively. The absorption band of the fabricated cells have shown a red shift due to the quantum confinement of the excitons present in the ZnO doped TiO2 compared to other nanopaste coated on FTO glass plate. This optical phenomenon of methanol treatment of Prunus Dulcis fruit, Red Indian Spinach leaves and Red

Indian Spinach fruit dyes dipped ZnO doped TiO2 nanopaste coated on FTO glass plate indicates that the maximum absorption peak appeared at around the region between 400 nm to 600 nm, around the region between 300 nm to 700 nm and around the region between 300 nm to 750 nm respectively. It was evident that the absorption of the ZnO doped TiO2 nanopaste coated dye dipped FTO glass plate exhibited the largest red shift compare to Bi, Al, Mg, Ag doped TiO2 and pure TiO2.

Figures 3.1.1 & 3.1.2: UV –Visible absorption spectra of Prunus Dulcis fruits & Red Indian Spinach leaves dye extracted by using different solvents

(A- methanol, B-ethanol and C- acetone).

Figure 3.1.3: UV –Visible absorption spectra of Red Indian Spinach fruit dye extracted by using different solvents (A- methanol, B-ethanol and C- ace-

tone).

Figure 3.1.4: UV –Visible absorption spectra of Prunus Dulcis fruits dye

dipped FTO glass plate extracted by using methanol solvent (A-ZnO-TiO2, B- Al-TiO2, C- Bi-TiO2, D-Mg-TiO2, E-Ag-TiO2 and F- pureTiO2)

26



Figures 3.1.5

Figures 3.1.6

Figures 3.1.5 & 3.1.6: UV –Visible absorption spectra of Red Indian Spinach leaves & fruit dye dipped FTO glass plate extracted by using methanol sol-vent (A-ZnO-TiO2, B- Al-TiO2, C- Bi-TiO2, D-Mg-TiO2, E-Ag-TiO2 and F- pure

TiO2)

3.2 Fourier Transform Infrared (FT-IR) Spectral Analysis The FT-IR spectra of Prunus Dulcis fruit, Red Indian Spinach leaves and Red Indian Spinach fruit dyes were recorded on Perkin Elmer spectrometer using KBr pellet technique in the range of 4000 – 400 cm-1. The FT-IR spectra of Prunus Dulcis fruit dye extracted by using different solvents such as methanol, ethanol and acetone to samples A, B and C is shown in figure 3.2.1. The strong peaks observed at 3420, 3435 and 3422 cm-1 are associated with O-H stretching vibration rising to both samples. The strong peak around at 1639 cm-1 may be caused by C=O stretching of carboxyl groups present in both samples. The small peaks at 1366 cm-1 were attributed to aldehyde group and peaks at 1218 cm-1 may arise by ether group as the presence of C-H bending. The very strong band arises at 3436 and 3430 cm-

1and it may be the presence of O-H stretching or NH2 stretching of amide groups in samples A and B only. The strong peak 1733 cm-1 is because of C=O stretching of aldihyde groups present at C sample. The band at 1638, 1645 and 1639 cm-1 peak is due to the presence of C=O stretching and C-N stretching groups in both samples. The

very small peaks at 691 cm-1 and 538 cm-1 are due to the presence of C-H bending groups in sample A & B only. The FT-IR spectra of Red Indian Spinach leaves dye extracted by using different solvent such as methanol, ethanol and acetone to samples A, B, and C as shown in figure 3.2.2. The vibrational mode of six C-C stretching at the peak 799 cm-1, 1207 cm-1, 1598 cm-1, 1615 cm-1 and 2295 cm-1, four C-H stretching at 3026 cm-1, 3077 cm-1, 3111 cm-1 and 3162 cm-1, CH2 asymmetric stretching at 3213 cm-1, one CH2 symmetric stretching at 3179 cm-1, six CH in plane stretching at 1258, 1428, 1462, 1473, 1530 and 1564 cm-1, four CH out of plane bending at 289, 782, 980 and 1000 cm-1, two C-N stretching at 986 and 1156 cm-1, one C-N in-plane bending at 578 cm-1, one C-N out of plane bending at 170 cm-

1, one CH2 wagging at 1225 cm-1, one CH2 twisting at 1190 cm-1, CH2 rocking at 884 cm-1, one CH2 scissoring at 1377 cm-

1 is observed at both samples. The weak absorption peak at 670 cm-1 and the peak at 3422 cm-1 is associated with –OH stretching vibration arises to sample A only. The strongest peak at 1530 cm-1, which is bending mode of C-H bonds only in B sample. The next strongest peak at 1462 cm-

1, corresponding to C-H stretching vibration and the peak at 2295 cm-1, which is corresponding to stretching mode of C-N triple bond are present in samples A & B only.

The FT-IR spectra of Red Indian Spinach fruits dye is extracted by using different solvents such as methanol, ethanol and acetone to samples A, B, and C as shown in figure 3.2.3. The very strong peak observed at the peak 3373 cm-1 and 3422 cm-1 may be due to the presence of bounded N-H and O-H stretching vibration present in both samples. The very strong peak observed at the peak 1639 cm-1 and 1366 cm-1 may be presence of C=O or C-N stretching in both samples. The weak band observed at 680 cm-1 is due to the presence of C-H bending groups in both samples. The weak band occurring at 700 cm-1 is due to C-H bending in samples A and B only. The strong bands around at 1644 cm-1 and 1397 cm-1 may be due to the presence of C=O stretching or C-N stretching groups in sample A only. The bands at 2959 and 2848 cm-1 may be due to C-H stretching of aliphatic groups in both samples.

Figure 3.2.1: FT-IR spectral analysis of Prunus Dulcis fruits dye extracted by using different solvents (A- methanol, B-ethanol and C- acetone).

27



Figure 3.2.2 FT-IR spectral analysis of Red Indian Spinach leaves and fruits dye extracted by using different solvents (A- methanol, B-ethanol and

C- acetone).

Figure3.2.3

Figure 3.2.3: FT-IR spectral analysis of Red Indian Spinach leaves and fruits dye extracted by using different solvents (A- methanol, B-ethanol and

C- acetone).

3.3 Photoluminescence (PL) Studies The photoluminescence studies of Prunus Dulcis fruit, Red Indian Spinach leaves, Red Indian Spinach fruit and Opuntia prickly pear fruit dyes were carried out by using PerkinEl-mer LS-55 luminescence spectrophotometer equipped with a Xenon lamp in the range of 200 nm– 1000 nm. An investi-gation on the photoluminescence studies of dyes is impor-tant as it can provide valuable information on the stability and purity of the dyes. The PL investigations yield informa-tion on the optical properties and the quality of synthesized material and particle absorbs photons and then reradiates photons. Photo excitation of a bulk semicon-ductor creates exciton, bound by weak columbic interaction. In PL spectra of Prunus Dulcis fruit dye is extracted by

using different solvents such as methanol, ethanol and ace-tone to samples A, B, and C as shown in figure 3.3.1. It exhib-its a sharp emission peak in the near UV region and a broad band in the visible region. In the samples A, B and C the peaks are observed at 510 nm in the green region, 490 nm in the blue is green region and 480 nm in the blueish green region respectively. In the PL spectra of Red Indian Spin-ach leaves dye extracted by using different solvent such as methanol, ethanol and acetone corresponding to samples A, B, and C is as shown in figure 3.3.2. It exhibits a sharp emis-sion peak in the near UV region and a broad band in the visi-ble region. In the sample A the three emission peaks observed are at 350 nm in the violet region, 520 nm in the green region and 610 nm in the yellow region. The first one corresponds to the band-edge emission. The second one is due to artifact. The third one arises from the singly ionized oxygen vacancy resulting in red emission of materials because of recombination of a photo generated hole with a singly ionized electron in valence band. In the sample B the three emission peaks observed are at 290 nm in the NBE region, 380 nm in the UV region and 590 nm in the yellow region. In the sample C the three emission peaks observed are at 280 nm in the NBE region, 380 nm in the UV region and 570 nm in the green region. The PL spectra of Red Indian Spinach fruit dye is extracted by using different solvents such as methanol, ethanol and acetone corresponding to samples A, B, and C as shown in figure 3.3.3. In the sample A the three emission peaks ob-served are at 400 nm in the violet region, 440 nm in the near blue region and 640 nm in the yellow region. In the sample B the two emission peaks observed are at 380 nm in the UV region and 550 nm in the green region. In the sample C the two emission peaks observed are at 370 nm in the UV region and 540 nm in the green region. In the sample A the peaks obtained are at high absorption at longer wavelength com-pared to other samples in all the dyes.

Figure 3.3.1: PL studies of Prunus Dulcis fruits dye extracted by using different solvents

(A- methanol, B-ethanol and C- acetone)

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Figure 3.3.2 PL studies of Red Indian Spinach leaves & fruits dye extracted by using different solvents (A- methanol, B-ethanol and C- acetone).

Figure 3.3.3: PL studies of Red Indian Spinach leaves & fruits dye extracted by using different solvents (A- methanol, B-ethanol and C- acetone).

3.4 Field Emission Scanning Electron Microscopy (FE-SEM) Analysis The FE-SEM analysis of dye dipped FTO glass plate coated on ZnO, Bi, Al, Mg, Ag doped TiO2 and pure TiO2 carried out by using the JEOL JSM-7500F model is an ultra high resolution field emission scanning electron microscope (FE-SEM) equipped with a high brightness conical FE gun and a low aberration conical objective lens. In the FE-SEM analysis was used to study a variety of surface effects present in em-bossed structures, thin film coatings, and polymeric sub-strates. The FE-SEM analysis of Prunus Dulcis fruit, Red In-dian Spinach leaves and Red Indian Spinach fruit dyes dipped FTO glass plate coated on various oxides doped TiO2 in methanol solvent is shown figures 3.4.1, 3.4.2 & 3.4.3 re-spectively. The film deposited from the sample A has larger grain size rather than of other samples. Due to its higher grain size, it exhibits lesser receptivity and also higher trans-parency which are important for TCO applications. It is clear that the prepared sample A has regular oval , spheri-cal shape and uniform size, good packing density with an average size of 30 nm and one can see some coalesced nanoparticles with a size of about 35 nm. The particles are spherical in shape with uniform size. It is clear from the image that titanium particles are evenly distributed on the surfaces without any aggregation. The TiO2 nanoparti-

cles formed were highly agglomerated. The spherical shaped particles with clumped distributions are visible through the FE-SEM analysis. It is clear that the prepared sample A has regular spherical shape and uniform size, good packing density compare to other samples. The FE- SEM micrograph shows that the morphology is replete with voids and pores, the cause of which can be traced to the large amounts of hot gases that escape out of the reaction mixture during combustion TiO2 with ZnO has wurtzite structure .

Figure 3.4.1 - The FE-SEM analysis of methanol treatment of Prunus Dulcis fruit dye dipped photo – anode (A-ZnO-TiO2, B- Al-TiO2, C- Bi-TiO2 , D-Mg-

TiO2, E-Ag-TiO2 and F- pure TiO2)

Figure3.4.2. The FE-SEM analysis of methanol treatment of Red Indian Spin-ach leaves dye dipped photo – anode (A-ZnO-TiO2, B- Al-TiO2, C- Bi-TiO2 , D-

Mg-TiO2, E-Ag-TiO2 and F- pure TiO2)

29



Figure 3.4.3 - The FE-SEM analysis of methanol treatment of Red Indian Spinach fruit dye dipped photo – anode (A-ZnO-TiO2, B- Al-TiO2, C- Bi-TiO2 ,

D-Mg-TiO2, E-Ag-TiO2 and F- pure TiO2)

3.5. Photocurrent-Voltage (I-V) Characteristics of the DSSC Photovoltaic measurements were carried out using a halogen light source that was focused to one sun at Air Mass (AM) 1.5, at the surface of the cells. The spectral output of the lamp was matched in the region 350 nm and 800 nm with the aid of a Schott KG-5 sunlight filter so as to reduce the mismatch between the stimulated and the true solar spectrum to less than 2%. The Prunus Dulcis fruit, Red Indian Spinach leaves & Red Indian Spinach fruit dyes dipped FTO glass plate coated on various oxides doped TiO2 in methanol solvent is shown figures 3.5.1, 3.5.2 & 3.5.3 and corresponding Tables 3.1, 3.2 & 3.3 respectively. The overall photo conversion efficiency (η) was calculated from the integral photocurrent density (Jsc), the open circuit photocurrent (Voc), the fill factor (ff) of the cell, and the in-tensity of the incident light (Pin) using the equation,

and Pin= 150 W/cm2 at AM 1.5,

Or under full sunlight and the fill factor (ff) is given by the equation .

Electronic coupling with ZnO doped TiO2 is best for Al and Bi doped TiO2 nanopaste coated photo-electrode. The importance of a blocking layer in controlling recombination with the electrolyte has already been pointed out but in the case of natural dyes, recombination with the oxidized dye can be relevant. The open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF) and conversion efficiency (η) as of fabricated cells are tabulated. By comparing minimum and maximum efficiency, the improvement in

short circuit current density is much higher than the open circuit voltage. So, efficiency of the cells is mainly attributed to the increased short circuit current density and results in power conversion efficiency enhancement. In the present study, sample A has higher conversion efficiency compared to the other samples.

Figure 3. 5. 1. J-V Curves of Prunus Dulcis fruit dye dipped FTO glass

plate

Table 3.1 Photovoltaic Parameters of Prunus Dulcis fruit dye dipped FTO glass plate (A-ZnO-TiO2, B- Al-TiO2, C- Bi-TiO2 , D-Mg-TiO2, E-Ag-TiO2

and F- pure TiO2)

Figure 3.5.2. J-V Curves of Red Indian Spinach leaves dye dipped FTO

glass plate

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Table 3.2 Photovoltaic Parameters of Red Indian Spinach leaves dye dipped FTO glass plate (A-ZnO-TiO2, B- Al-TiO2, C- Bi-TiO2, D-Mg-TiO2, E-

Ag-TiO2 and F- pure TiO2)

Figure 3.5.3 J-V Curves of Red Indian Spinach fruits dye dipped FTO

glass plate

Table 3.3 Photovoltaic Parameters of Red Indian Spinach fruits dye dipped FTO glass plate (A-ZnO-TiO2, B- Al-TiO2, C- Bi-TiO2, D-Mg-TiO2, E-

Ag-TiO2 and F- pure TiO2)

4. CONCLUSION

In conclusion, it is asserted that from the UV-Visible absorption spectra of Prunus Dulcis fruit, Red Indian Spinach leaves and Red Indian Spinach fruit dyes, small band gaps were seen in the entire visible region compared to other solvent effects so it is a good condition for the sensitized cells. All natural dyes having different functional groups and vibration assignment have been carried out by FT-IR spectral analysis. The PL spectra of the natural dyes in methanol solvent give the relationship between solar energy conversion efficiency and spectroscopic properties. The FE-SEM results give the average particle size of pure and synthesized nanoparticles measured as 30 nm and 25

nm. The photovoltaic measurements were carried out the Voc, Jsc, Vmax, Jmax, FF and overall energy conversion efficiency (η) of the prepared dye- sensitized using Prunus Dulcis fruit, Red Indian Spinach leaves and Red Indian Spinach fruit dyes. This improvement of NDSSCs from pure TiO2 to ZnO doped TiO2 nano powder has good economy, low resistance, high reflectance and simple fabrication processes. Experimental results clearly show that the efficiency of DSSCs gradually increased from pure TiO2 to ZnO doped TiO2 fabricated cells. The improved photoelectric conversion efficiency from 0.36 % to 0.96 % was obtained from these cells. Finally, it may be concluded that the sample-A showed excellent solar energy conversion efficiency compared to other samples for all natural dyes.

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Sensitizers Performance of Dye-Sensitized Solar Cells Fabricated With Indian Fruits and Leaves

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