Five aldimine derivatives were prepared by condensation of the appropriate amine with salicylaldehyde (m1-m4) and 4-aminobenzoic acid with 2-thiophene carboxaldehyde (m5). A molar ratio of 1: 1 was used and the mixture was refluxed in ethanol for 2 h to obtain the corresponding aldimine derivative. These derivatives were used as photosensitizers for dye-sensitized solar cells (DSSCs). The best performance was obtained for the DSSC sensitized with 2-(2-hydroxybenzylideneamino) benzoic acid, for which a short-circuit current of 2.86 mA/cm^ 2, an open-circuit voltage of 0.562 V, and an efficiency of 0.575% were obtained.Five aldimine derivatives were prepared by condensation of the appropriate amine with salicylaldehyde (m1-m4) and 4-aminobenzoic acid with 2-thiophene carboxaldehyde (m5). A molar ratio of 1: 1 was used and the mixture was refluxed in ethanol for 2 h to obtain the corresponding aldimine derivative. These derivatives were used as photosensitizers for dye-sensitized solar cells (DSSCs). The best performance was obtained for the DSSC sensitized with 2-(2-hydroxybenzylideneamino) benzoic acid, for which a short-circuit current of 2.86 mA/cm^ 2, an open-circuit voltage of 0.562 V, and an efficiency of 0.575% were obtained

Abdel-Latif, Monzir S.

Batniji, Amal Y.

El-Agez, Taher M.

El-Ghamri, Hatem S

Morjan, Rami Y.

Taya, Sofyan A.

English

Institutional Repository of the Islamic University of Gaza

Turk J Phys(2014) 38: 86 { 90c TUB_ITAKdoi:10.3906/z-1309-4Turkish Journal of Physicshttp :// journa l s . tub i tak .gov . t r/phys i c s/Research ArticleAldimine derivatives as photosensitizers for dye-sensitized solar cellsAmal Y. BATNIJI1, Rami MORJAN2, Monzir S. ABDEL-LATIF2,Taher M. EL-AGEZ1, Sofyan A. TAYA1;, Hatem S. EL-GHAMRI11Physics Department, Islamic University of Gaza, Gaza, Palestinian Authority2Chemistry Department, Islamic University of Gaza, Gaza, Palestinian AuthorityReceived: 22.09.2013  Accepted: 06.12.2013  Published Online: 17.01.2014  Printed: 14.02.2014Abstract: Five aldimine derivatives were prepared by condensation of the appropriate amine with salicylaldehyde(m1{m4) and 4-aminobenzoic acid with 2-thiophene carboxaldehyde (m5). A molar ratio of 1:1 was used and themixture was reuxed in ethanol for 2 h to obtain the corresponding aldimine derivative. These derivatives were used asphotosensitizers for dye-sensitized solar cells (DSSCs). The best performance was obtained for the DSSC sensitized with2-(2-hydroxybenzylideneamino)benzoic acid, for which a short-circuit current of 2.86 mA/cm2 , an open-circuit voltageof 0.562 V, and an eciency of 0.575% were obtained.Key words: Dye-sensitized solar cell, TiO2 , aldimine derivatives1. IntroductionThe direct conversion of sunlight into electrical power by solar cells is one of the most promising future energyproduction techniques. Dierent from many other electrical energy production techniques, solar cells are ofparticular interest because electricity is produced without the exhaust of greenhouse gases. Dye-sensitized solarcells (DSSCs) were rst announced as an innovative solar energy conversion technology in 1991. They are foundto have many advantages, such as that they are a cheap, renewable, and environmentally acceptable sourceof energy production [1{5]. A DSSC has a very simple structure. It consists of a sensitizing dye chemicallyanchored to a nanocrystalline wide band-gap semiconducting material, such as TiO2 or ZnO. A high surfacearea for dye coverage is provided by the mesoporosity of the semiconducting material. This allows the capturingof the majority of the incident solar energy by the adsorbed dye monolayer. The cell is illuminated through atransparent conductive oxide electrode such as uoride-doped tin oxide (FTO). The semiconducting materialin paste formulation is deposited onto the FTO layer. The porous photoanode is usually immersed in a redoxelectrolyte I =I 3 and is electrically connected to a counter electrode. When the DSSC is illuminated, electronsare absorbed by the dye and injected into the semiconductor conduction band, and they move through the FTOsubstrate to the external load. The oxidized dye is reduced by the electrolyte, which transports the positivecharges to the counter electrode.The eciency of a DSSC depends on many factors, such as a delicate balance of the kinetics for injection,dye regeneration, and recombination reactions [4]. The sensitizing dye behaves as a solar energy absorber. Anideal sensitizer should have a set of features to make the DSSC ecient. It should absorb all the light below athreshold wavelength of about 920 nm. Moreover, it should be rmly grafted to the semiconducting materialCorrespondence: staya@iugaza.edu.ps86BATNIJI et al./Turk J Physsurface and inject electrons into the conduction band with a quantum yield of unity. Another importantparameter is the dye redox potential, which should be high enough so that it can be regenerated rapidlyvia electron donation from the electrolyte. Finally, it should be stable enough to sustain at least 108 redoxturnovers under illumination, corresponding to about 20 years of exposure to natural light. The best photovoltaicperformance in terms of both conversion yield and long-term stability has so far been achieved with polypyridylcomplexes of ruthenium and osmium. The sensitizers used in DSSCs are divided into 2 types, organic andinorganic dyes, according to the structure. Inorganic dyes include metal complexes, such as polypyridylcomplexes of ruthenium and osmium, metal porphyrin, phthalocyanine, and inorganic quantum dots, whileorganic dyes include natural and synthetic organic dyes. So far, devices based on ruthenium polypyridylsensitizers and an iodide/triiodide redox mediator exhibit an eciency of about 11% [6]. Many researchers havedeveloped synthetic dyes for the fabrication of ecient DSSCs [7,8]. Dai et al. presented DSSCs fabricatedusing TiO2 photosensitized by adsorbed anthocyanin dyes with iodide/iodine in water at pH 1 [7]. In 2009, theuse of a diazapentadiene derivative and 2 compounds of triazole derivatives as photosensitizers of DSSCs wasachieved [8]. Intensive research has been carried out to fabricate DSSCs using natural dyes [9,10].In this work, DSSCs are fabricated and studied using aldimine derivatives as sensitizing dyes. These dyeswere prepared by condensation of the appropriate amine with salicylaldehyde or thiophene carboxaldehyde. Amolar ratio of 1:1 was used and the mixture was reuxed in ethanol for 2 h to obtain the corresponding aldiminederivative.2. Experiment2.1. Preparation of dye sensitizersFive aldimine derivatives (Figure 1) were prepared by condensation of the appropriate amine with salicylaldehyde(m1{m4) and 4-aminobenzoic acid with 2-thiophene carboxaldehyde (m5). A 1:1 molar ratio was used andthe mixture was reuxed in ethanol for 2 h to obtain the corresponding aldimine derivative. The obtainedderivatives were 2-((phenylimino)methyl)phenol (m1), 2-(2-hydroxybenzylideneamino)benzoic acid (m2), 2-(2-hydroxybenzylideneamino)phenol (m3), 4-(2-hydroxybenzylideneamino)benzoic acid (m4), and N-(thiophen-2-ylmethylene)aniline (m5).2.2. Preparation of dye-sensitized solar cellsFTO conductive glass sheets with sheet resistance of 15 /square and transmission of >80% (Xinyan Tech-nology Ltd., Hong Kong) were rst cut into small pieces of dimensions 1 cm  1 cm. The pieces were cleanedin an ultrasonic bath for 15 min, rinsed with water and ethanol, and then dried. TiO2 paste was prepared byadding 50 mg of TiO2 nanopowder, 10{25 nm (US Research Nanomaterial, Inc., USA), to 50 mg of polyethyleneglycol; the mixture was then ground for 30 min in a mortar until a homogeneous paste was obtained. The pastewas deposited on the FTO conductive glass by doctor-blade technique in order to obtain a TiO2 layer of 0.25cm2 in area. The TiO2 layer was preheated at 60C for 20 min and then sintered at 450 C for 30 min.After cooling down to 60 C, the sheets with TiO2 thin lm layer were immersed in a solution of the aldiminederivatives for 24 h. The dyed TiO2 layer and a sputtered platinum counter electrode were assembled to forma solar cell by sandwiching a redox (I /I 3 ) electrolyte solution. The electrolyte solution was composed of 2mL of acetonitrile, 8 mL of propylene carbonate, 0.668 g of KI, and 0.0634 g of I2 .87BATNIJI et al./Turk J PhysFigure 1. Chemical structures of the aldimine photosensitizers.2.3. MeasurementsThe UV-VIS absorption spectra of all aldimine derivatives were measured using a UV-VIS spectrophotometer(GENESYS 6, Thermo Scientic, USA). The absorption spectrum analysis was carried out in the wavelengthrange from 400 to 800 nm. The J V characteristic curves under illumination were established using a NationalInstruments data acquisition card (USB NI 6251) in combination with the LabVIEW program. The J   Vcurves were measured at 100 mW/cm2 irradiation using a high-pressure mercury arc lamp.3. Results and discussionFigure 2 illustrates the absorption spectra of 2-((phenylimino)methyl)phenol (m1), 2-(2-hydroxybenzylideneami-no)benzoic acid (m2), 2-(2hydroxybenzylideneamino) phenol (m3), 4-(2-hydroxybenzylideneamino)benzoic acid(m4), and N-(thiophen-2-ylmethylene)aniline (m5) using ethyl alcohol as a solvent. As can be seen from thegure, the absorption peaks of all dyes lie in the spectral region having a wavelength of less than 500 nm.400 500 600 700 8000.00.20.40.60.81.01.21.4Absorption (a.u.)Wavelength (nm)m1m2 m 3 m 4 m 5Figure 2. The absorption spectra of all aldimine derivatives.88BATNIJI et al./Turk J PhysThe J -V characteristic curves of the 5 DSSCs dyed with aldimine derivatives were established underillumination with white light of intensity 100 mW/cm2 from a high-pressure mercury arc lamp. These curvesare shown in Figure 3. The DSSC output power was calculated as P = JV using the J V data correspondingto each cell. The output power plotted as a function of V is shown in Figure 4 for all cells. The photocurrent(Im) and photovoltage (Vm) corresponding to the maximum power point (Pm) were then obtained for each cellfrom the P -V curve. The values of the ll factor (FF ) and the cell eciency () were then calculated using:FF =Im VmIsc Voc; (1) =FF Isc VocPin; (2)where Im and Vm are the photocurrent and photovoltage for maximum power output and Isc and Voc are theshort-circuit photocurrent and open-circuit photovoltage, respectively. Pin is the power of incident light.0.0 0.1 0.2 0.3 0.4 0.5 0.6–2.8–2.4–2.0–1.6–1.2–0.8–0.40.0m1m2 m3m4m5J(mA/cm2)Voltage (V)0.0 0.1 0.2 0.3 0.4 0.50.00.10.20.30.40.50.6 m 1m2m3 m 4 m 5Power (mW)Voltage (V)Figure 3. J   V characteristic curves for the fabricatedDSSC sensitized using TiO2 nanoparticle as semiconduc-tor.Figure 4. Power versus voltage curves for all cells.All results are summarized in the Table. It is clear that the short-circuit current ranged from 0.159 to 2.86mA/cm2 for the DSSCs sensitized with 2-((phenylimino)methyl)phenol (m1) and 2-(2-hydroxybenzylideneamino)benzoic acid (m2), respectively. The short-circuit currents obtained for the DSSCs sensitized with 2-(2-hydroxybenzylideneamino)phenol (m3), 4-(2-hydroxybenzylideneamino)benzoic acid (m4), and N-(thiophen-2-ylmethylene)aniline (m5) were, respectively, 0.169, 0.700, and 0.210 mA/cm2 . The open-circuit voltageranged from 0.218 V for the DSSC sensitized with 2-((phenylimino)methyl)phenol (m1) to 0.562 V for thatsensitized with 2-(2-hydroxybenzylideneamino)benzoic acid (m2). Moreover, the DSSC sensitized with 4-(2-hydroxybenzylideneamino)benzoic acid (m4) exhibited a relatively high open-circuit voltage of 0.539 V. Othercells sensitized with 2-(2-hydroxybenzylideneamino)phenol (m3) and N-(thiophen-2-ylmethylene)aniline (m5)showed low open-circuit voltages of 0.2 and 0.3 V. The conversion eciency of the fabricated cells ranged from0.007% for the cell sensitized with 2-((phenylimino)methyl)phenol (m1) to 0.575% for that sensitized with 2-(2-hydroxybenzylideneamino)benzoic acid (m2). Therefore, it is clear that 2-(2-hydroxybenzylideneamino)benzoicacid (m2) is a strong candidate as a sensitizer for ecient DSSCs.89BATNIJI et al./Turk J PhysTable. Photoelectrochemical parameters of the DSSCs sensitized by various chemical dyes.DyeJsc Voc Jm Vm Pmax %(mA/cm2) (V) (mA/cm2) (volt) (mW)m1 0.159 0.218 0.051 0.141 0.007 0.007m2 2.86 0.562 1.599 0.339 0.575 0.575m3 0.169 0.219 0.052 0.140 0.0075 0.0075m4 0.700 0.539 0.333 0.383 0.127 0.127m5 0.210 0.339 0.102 0.180 0.0185 0.01854. ConclusionFive aldimine derivatives were prepared and examined as sensitizers for ecient dye-sensitized solar cells. A rela-tively high open-circuit voltage was obtained for the DSSCs sensitized with 2-(2-hydroxybenzylideneamino)benzoicacid (m2) and 4-(2-hydroxybenzylideneamino)benzoic acid (m4). A relatively high short-circuit current was ob-tained for the DSSC sensitized with 2-(2-hydroxybenzylideneamino)benzoic acid (m2). We suggest that aldiminederivatives such as 2-(2-hydroxybenzylideneamino)benzoic acid (m2) would be strong candidates for fabricatinglow-cost and ecient dye-sensitized solar cells.AcknowledgmentThis project was nancially supported by the Deanship of Research Aairs of the Islamic University of Gazafor the 2012 calendar year.References[1] O'Regan, B.; Gratzel, M. Nature 1991, 353, 737{740.[2] Gledhill, S. E.; Scott, B.; Gregg, B. A. J. Mater. Res. 2005, 20, 3167{3169.[3] Abdel-Latif, M. S.; El-Agez, T. M.; Taya, S. A.; Batniji, A.Y.; El-Ghamri, H. S. Material Sciences and Applications2013, 4, 516{524.[4] Haque, S. A.; Palomares, E.; Palomares, E.; Cho, M. B.; Green, A.N.; Hirata, N., Klug, D. R.; Durrant, J. R. J.Am. Chem. Soc. 2005, 127, 3456{3462.[5] Zhao, W.; Hou, Y. J.; Wang, X. S.; Zhang, B. W.; Cao, Y.; Yang, R.; Wang, W. B.; Xiao, X. R. Sol. Energ. Mat.Sol. C. 1999, 58, 173{183.[6] Chiba, Y.; Islam, A.; Watanabe, Y.; Komiya, R.; Koide, N.; Han, L. Jpn. J. Appl. Phys. 2006, 48, L638{L640.[7] Dai, Q.; Rabani, J. J. Photoch. Photobio. A 2002, 26, 421{426.[8] El-Agez, T. M.; El Tayyan, A. A.; Abdel-Latif, M. S. Journal of the Islamic University of Gaza 2009, 17, 61{70.[9] El-Agez, T. M.; El Tayyan, A. A.; Al-Kahlout, A.; Taya S. A.; Abdel-Latif, M. S. International Journal of Materialsand Chemistry 2012, 2, 102{107.[10] Taya, S. A.; El-Agez, T. M.; El-Ghamri, H. S.; Abdel-Latif, M. S. International Journal of Material Sciences andApplications 2013, 2, 37{42.90

Aldimine derivatives as photosensitizers for dye-sensitized solar cells

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Aldimine derivatives as photosensitizers for dye-sensitized solar cells

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