Effect of Ni doping into chlorophyll dye on the

Effect of Ni doping into chlorophyll dye on the efficiency of dye-sensitized solar cells (DSSC) D. D. Pratiwi, F. Nurosyid, Kusumandari, A. Supriyanto, and R. Suryana

Citation: AIP Conference Proceedings 2014, 020066 (2018); doi: 10.1063/1.5054470 View online: https://doi.org/10.1063/1.5054470 View Table of Contents: http://aip.scitation.org/toc/apc/2014/1 Published by the American Institute of Physics

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Effect of Ni Doping into Chlorophyll Dye on the Efficiency of Dye-Sensitized Solar Cells (DSSC) D. D. Pratiwi1, a) , F. Nurosyid1, 2, b), Kusumandari1, 2, A. Supriyanto1, 2, and R. Suryana1, 2 1

Physics Department, Graduate Program, Universitas Sebelas Maret,, Jl. Ir. Sutami 36A Kentingan Surakarta 57126, Indonesia 2 Physics Department, Faculty of Mathematics and Natural Sciences, Universitas Sebelas Maret, Jl. Ir. Sutami 36A Kentingan Surakarta 57126, Indonesia a)

[email protected] b) [email protected]

Abstract. This article reported the effect of metal doping into natural dye on the performance of photosensitizer and DSSC efficiency. Natural dye was extracted from spinach leaves and nickel (II) chloride used as metal. The concentration of metal were varied of 0.01 M, 0.05 M, and 0.5 M. The absorbance of dye solutions and the dye adsorption on the TiO 2 electrodes were characterized by UV-Vis spectroscopy. The electrical characteristic of dye solutions and DSSCs were measured using I-V meter. As a result, the absorbance of dye solutions increased in the wavelength above 700 nm. This region was light absorption of Ni metal. Increasing the concentration of Ni into chlorophyll dye also increased the value of conductivity. The optimum efficiency of DSSC was obtained at a concentration of 0.05 M, with the efficiency value was 0.0769%. This result was also supported by the highest absorbance of dye adsorption on the TiO 2 electrode at a concentration of 0.05 M. The efficiency of DSSC increased up to 135% as compared to pure chlorophyll dye.

INTRODUCTION One of solar cell types is dye-sensitized solar cells (DSSC). DSSC is a semiconductor device based on the sensitization that converts light energy into electrical energy [1 – 3]. The DSSC offers the advantages such as easy and simple fabrication process, the material is easy to obtain, and can be made flexible device [1, 4 – 5]. The DSSC components consists of a transparent conducting oxide (TCO) glass substrate, photoanode, the dye sensitizer, electrolyte, and counter electrode. Fluorine doped tin oxide (FTO) or indium doped tin oxide (ITO) is commonly used as TCO. The photoanode using titanium dioxide (TiO2), zinc oxide (ZnO), tin oxide (SnO2), and niobium oxide (NbO). The materials which commonly used as a counter electrode are platinum (Pt), graphite (C), conductive polymer etc [6 – 8]. The dye sensitizer can be used from synthetic and natural dyes. The major types of electrolytes using the liquid electrolyte, solid-state electrolyte, quasi-solid electrolyte, and polymer [9 – 11]. The dye sensitizer is one of the key components of DSSC that playing important role. The dye sensitizer acts as absorber and converter the light energy into electrical energy [12 – 14]. The sensitizers are mainly grouped into three types; metal complex sensitizer, metal-free organic sensitizer, and natural sensitizer. The most common of metal complex types are N3, N719, and black dye (N749). The conversion efficiency of DSSC with these metal complex were 10%, 11.18%, and 11.1%, respectively [15 – 16]. The common design of metal-free organic sensitizer is a donor-acceptor-substituted π-conjugated bridge (D-π-A). It has been reported to present conversion efficiency of 13% [17]. The synthetic sensitizers provide relatively high efficiencies. However, they have several problems such as high cost, limited color various, and presence of heavy metals that are not environmentally friendliness. The natural sensitizer is an alternative key to produce low cost and environmentally friendliness dyes [18 – 19].

International Conference on Science and Applied Science (ICSAS) 2018 AIP Conf. Proc. 2014, 020066-1–020066-7; https://doi.org/10.1063/1.5054470 Published by AIP Publishing. 978-0-7354-1730-4/$30.00

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The benefits of natural sensitizers are due to their cost-effective production, presence of various the pigments color, simple extraction method, complete biodegradation, easy and high availability from the environment [18 – 24]. The part of plants can be utilized as a natural pigment such as flowers, fruits, leaves, seeds, and rind. The natural sensitizer are classified as carotenoids, betalains, flavonoids, anthocyanin, and chlorophyll [25 – 26]. Kumara et al. have identified the utilization of natural dye as photosensitizer in DSSC application [26]. The chlorophyll pigment from rhubarb resulted the efficiency of 0.0104%. Carotenoid pigment was also succesfully extracted from turmeric as a photosensitizer DSSC and yielded a conversion efficiency of 0.03% [25]. Wongcharee et al. reported the efficiency of 0.05% using blue pea extract as an anthocyanin dye [27]. Based on these studies, the researchers began to develop the natural dye modification. It aims to increase the performance of natural dye. Pratiwi et al. (2017) mixing the natural dyes from chlorophyll and anthocyanin pigments. As a result, efficiency of DSSC increased three times as compared to single dye [28]. Puspitasari et al. also used the dyes mixture from three different pigments and achieved the conversion efficiency up to five times from single dye [29]. In addition, Fadli et al. investigated the Cu metal doping into natural dye and resulting the efficiency of DSSC twice as much as compared to pure natural dye [30]. This article describes the study of natural dye modification by metal doping method. The method of metal doping is carried out by inserting the Ni metal into chlorophyll dye. This method is one of the efforts to increase the dye conductivity. The success of metal doping into the dye is affected by various factors such as the number of metal concentration, the pH and temperature of metal doping, and the time of stirring. This article is focused the effect of metal concentration on the performance of photosensitizer and DSSC efficiency. METHODS Fluorine Doped Tin Oxide (FTO) from Dyesol with size of 2 cm x 2 cm and 18NR-T Transparent Titania (TiO2) from Dyesol were used as transparent conductive glass subtrates and working electrode, respectively. The TiO2 paste was deposited on the FTO conductive glass by spin coating technique. The chlorophyll dye was extracted from spinach leaves. The leaves were cleaned using distilled water and crushed using mortar. The crushed mass were dissolved into the ethanol solvent. The solution was stirred to get homogeneous solution. The Ni metal was dissolved into chlorophyll dye with various concentration of 0.01 M, 0.05 M, and 0.5 M. After stirred for 30 minutes, it were used for immersion the working electrode. The counter electrodes from hexachloroplatinic (IV) acid solution were coated using platinum catalyst by brush painting technique. Finally, fabrication of DSSCs prototype with effective cell area of 0.75 cm2 into the sandwich structure. The working and counter electrodes were combined with scotch tape at 76 μm of intervals. The electrolyte solution made from the mixture of polyethylene glycol (PEG) 400, potassium iodide (KI), and iodine (I2) was filled in the space between electrodes. The absorbance of dye solutions and dye adsorption on the TiO2 electrodes were analyzed by UV-Vis spectrophotometer Lambda 25. The electrical conductivity of dye solutions and photocurrent-photovoltage of DSSCs were measured by Keithley I-V Meter 2602A.

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RESULTS AND DISCUSSIONS Characterization of Dye Solutions

Pure chlorophyll dye

4

Chlorophyll + Ni 0.01 M Chlorophyll + Ni 0.05 M

3.5

Chlorophyll + Ni 0.5 M

Absorbance

3 2.5 2 1.5 1 0.5 0 400

450

500

550

600

650

700

750

800

Wavelength (nm) FIGURE 1. UV-Vis absorption spectra of chlorophyll dye and dye doped Ni solutions with various concentrations

Figure 1 revealed absorption spectrum of chlorophyll dye and dye doped Ni solutions with various concentrations at wavelength of 400 – 800 nm. The light absorption of pure chloropyll dye at the wavelength range of 400 – 490 nm and 630 – 700 nm. Having absorption in the visible spectrum indicate the dye suitable as photosensitizer for DSSC application. Next, the absorbance of dye significantly increase after doped with Ni 0.01 M. However, the absorbance at 600 – 700 nm slightly decrease after doped with Ni 0.05 M and 0.5 M. The wavelength region above 700 nm showed the light absorption of Ni. Increasing the number of Ni concentration also increased the light absorption as compared to pure chlorophyll dye. The absorption of light was absorbed by the dye wider, then the excitation of electron from HOMO to LUMO levels also increased.Thus it was expected the producing current was also greater. The various concentrations of Ni into chlorophyll dye were not affect the position of absorbance peak but affected the absorbance value. The electrical characteristic (conductivity) of dye solution was measured using Keithley I-V Meter with light intensity of 1000 W/m2. The conductivity of dye doped Ni solutions with various concentrations are shown in Fig. 2.

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0.014 Pure chlorophyll dye Chlorophyll + Ni 0.01 M Chlorophyll + Ni 0.05 M Chlorophyll + Ni 0.5 M

0.012

I (Ampere)

0.01 0.008 0.006 0.004 0.002 0 0

1

2

3

4

5

V (Volt)

FIGURE 2. I-V curve for chlorophyll dye and dye doped Ni solutions with various concentrations

The conductivity value of pure chlorophyll dye of 0.0132 Ω m-1, while chlorophyll dye doped Ni with concentrations of 0.01 M, 0.05 M, and 0.5 M obtained the conductivity value of 0.0796 Ω m-1, 0.163 Ω m-1, and 0.331 Ω m-1, respectively. The photocoductivity activity of chlorophyll dye solution increased continuosly with increasing the concentration of Ni metal. It suggests that Ni doping into chlorophyll dye has the ability to produce the good electrical currents. Efficiency of DSSCs Figure 3 is a characteristic curve of I-V DSSCs based on dye chlorophyll and dye doped Ni with various concentration. The current-voltage (I-V) was measured by Keithley I-V Meter 2602A System Source. The measurements were performed in dark and light conditions by Xenon with light intensity of 1000 W/m2.

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0.0001 Voc Vmax

I (Ampere)

0

-0.0001 Imax Isc

-0.0002

-0.0003

Pure chlorophyll dye Chlorophyll + Ni 0.01 M Chlorophyll + Ni 0.05 M Chlorophyll + Ni 0.5 M

-0.0004 -0.4

-0.2

0

0.2

0.4

V (Volt) FIGURE 3. I-V curve for DSSCs sensitized by chlorophyll dye and dye doped Ni with various concentration

The I-V curve was used to determine the DSSC performance. The DSSC perfomance consists of Vmax, Imax, Voc, Isc, FF, and efficiency (η). The efficiency of DSSC is very important parameter and it represents a relation between the number of electron-hole pair produced to number of photons incident on the cell. The efficiency of DSSC can be calculated by the following equation: η=

100% =

100% =

100%

(1)

The power input (Pin) is obtained from multiplication between the light intensity and effective cell area. The efficiency of DSSCs were listed in Table 1. TABLE 1. Efficiency of DSSCs based on dye chlorophyll and dye doped Ni with various concentration. Dye η (%)

Pure Chloropyll

0.0326

Chloropyll + Ni 0.01 M

0.0337

Chloropyll + Ni 0.05 M

0.0769

Chloropyll + Ni 0.5 M

0.0287

Table 1 represented that the DSSC obtained the best performance at the metal concentration of 0.05 M and decreased at high concentration of 0.5 M. This phenomenon was called the metal bulk effect. DSSC performance achieved the optimum efficiency at a certain amount of concentration, and decreased at a higher concentration level. This results corresponded to the dye adsorption on the TiO2 eletrode as shown in Fig.4.

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0.14 Pure chlorophyll dye Chlorophyll + Ni 0.01 M

0.12

Chlorophyll + Ni 0.05 M Chlorophyll + Ni 0.5 M

Absorbance

0.1 0.08 0.06 0.04 0.02 0 400

450

500

550

600

650

700

750

800

Wavelength (nm) FIGURE 4. UV-Vis absorption spectra of dye adsorbed on the TiO2 electrodes

Increasing the concentrations of Ni doping also increased the current as compared to pure chlorophyll dye, while the efficiency of DSSC decreased at highest concentration. This result can be explained by the precipitation effect on the TiO2 electrode. This phenomenon involved the number of inactive dye molecules on the TiO 2 electrode, although the UV-Vis and conductivity results of dye solutions performed a continuous increase with increasing the concentration. However, when the TiO2 electrodes were immersed into dye doped Ni at high concentration showing the low absorbance. Since low interaction of dye molecules on the TiO 2 electrode, it preventing the number of electrons injection. In contrast, the metal concentration of 0.05 M has good interaction between the number of active dye molecules with the TiO2 surface. Dye doped Ni at a concentration of 0.05 M yielded the highest efficiency and absorbance of dye adsorption on the TiO2 electrode. The Ni doping into chlorophyll increased the efficiency up to 135% as compared to pure chlorophyll dye. This result was better than the previous study used Cu doping into anthocyanin, which the efficiency up to 71% as compared to anthocyanin dye [30]. SUMMARY The Ni was successfully doped into chlorophyll dye for the fabrication of DSSC with various concentrations of 0.01 M, 0.05 M, dan 0.5 M. The absorbance and electrical conductivity of chlorophyll increased proportionally with the concentrations of Ni. The highest efficiency of 0.0769% was obtained at the concentration of 0.05 M of Ni or about 135% as compared to pure chlorophyll dye. ACKNOWLEDGEMENTS This work was supported by Higher Education and Institute for Research and Community services. Universitas Sebelas Maret by PU UNS Grant Program (Contract Number: 543/UN27.21/PP/2018).

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