Characteristics of triphenylamine-based dyes with multiple acceptors in application of dye-sensitized solar cells

We report the synthesis and photophysical/electrochemical properties of triphenylamine (TPA)-based multiple electron acceptor dyes (TPAR1, TPAR2, and TPAR3) as well as their applications in dye-sensitized solar cells (DSSCs). In these dyes, the TPA group and the rhodanine-3-acetic acid play the role of the basic electron donor unit and the electron acceptor, respectively. It was found that introduction of two rhodanine-3-acetic acid groups into the TPA unit (TPAR2) exhibited better photovoltaic performance due to the increase with a red shift and broadening of the absorption spectrum. The monolayer of these TPA-based dyes was adsorbed on the surface of nanocrystalline TiO₂ mesoporous electrode with the thickness of ∼6 μm, polyethylene oxide (PEO) used as the matrix of gel electrolyte, and 4-nm thick Pt used as a counter-electrode. Photovoltaic device can be realized in a single quasi-solid-state DSSC. TPAR2-based gel DSSC had an open circuit voltage and short circuit current density of about 541 and 10.7 mA cm⁻², respectively, at 1-sun.     

Influence of acceptor moiety in triphenylamine-based dyes on the properties of dye-sensitized solar cells

Triphenylamine-based organic dyes with different acceptor parts have been synthesized in an attempt to investigate the effect of the acceptor moiety on the properties of dye-sensitized solar cells. The light-to-electricity conversion efficiencies of 4.67% and 5.05% were obtained for the DSCs based on 2-(4-oxo-5-(4-(phenyl(4-styrylphenyl)amino)benzylidene)-2-thioxothiazolidin-3-yl)acetic acid (TPAR11) and 2-cyano-3-(4-(phenyl(4-styrylphenyl)amino)phenyl)acrylic acid (TC12), respectively. A molecular-orbital calculation shows that the delocalization of the excited state for TPAR11 is broken between the 4-oxo-2-thioxothiazolidine ring and the acetic acid, which affects the electron movement from dye molecule to the semiconductor film. The effects of chenodeoxycholic acid (CDCA) as the coadsorbent on the photovoltaic performance of the DSCs based on TPAR11 and TC12 have been also studied. It has been found that the addition of 1 mM CDCA coadsorbent improves the photocurrent for TPAR11 and the photovoltage for TC12, owing to the suppression of the quenching processes of the excited electrons between dye molecules or/and a more negative conductive band edge of TiO₂ film. With the addition of 1 mM CDCA, the light-to-electricity conversion efficiencies of the DSCs based on TPAR11 and TC12 were 5.46% and 5.96%, respectively. This result indicates that both the acceptor moiety of metal-free organic dyes and the coadsorbent added in the electrode preparation have the effect on the photovoltaic performance of DSCs.     

Low band gap dyes based on 2-styryl-5-phenylazo-pyrrole: Synthesis and application for efficient dye-sensitized solar cells

A new series of low band gap dyes, C1, C2 and S, based on 2-styryl-5-phenylazo-pyrrole was synthesized. These dyes contain one carboxy, two carboxy and one sulfonic acid anchoring groups, respectively. They were soluble in common organic solvents, showed long-wavelength absorption maximum at ∼620 nm and optical band gap of 1.66-1.68 eV. The photophysical and electrochemical properties of these dyes were investigated and found to be suitable as photosensitizers for dye sensitized solar cells (DSSCs). The quasi solid state DSSCs with dye S showed a maximum monochromatic incident photon to current efficiency (IPCE) of 78% and an overall power conversion efficiency (PCE) of 4.17% under illumination intensity of 100 mW cm⁻² (1.5 AM), which is higher than the other dyes (3.26% for C2 and 2.59% for C1). Even though dye S contains one sulfonic acid anchoring group, the higher PCE for the DSSCs based on this dye has been attributed to the higher dye loading at the TiO₂ surface and enhanced electron lifetime in the device, as indicated by absorption spectra and electrochemical impedance spectra measurements. Finally, by increasing the molecular weight of poly(ethylene oxide) (PEO) in electrolyte, the PCE also increases up to 4.8% for the electrolyte with PEO molecular weight of 2.0 × 10⁶. This improvement has been attributed to the enhancement in iodide ions diffusion due to the increase in free volume of polymer gel electrolyte.     

Nano-sized Ag-inserted amorphous ZnSnO3 multilayer electrodes for cost-efficient inverted organic solar cells

A sheet resistance- and optical transmittance-tunable amorphous ZnSnO₃ (ZTO) multilayer electrode created through the insertion of a nano-scale Ag layer is demonstrated as an indium-free transparent conducting electrode for cost-efficient inverted organic solar cells (IOSCs). Due to the antireflection effect, the ZTO/Ag/ZTO/glass exhibited a high transmittance of 86.29% in the absorption wavelength region of the organic active layer and a low resistivity of 3.24×10⁻⁵ Ω cm, even though the ZTO/Ag/ZTO electrode was prepared at room temperature. The metallic conductivity of the electrode indicates that its electrical conductivity is dominated by the nano-scale Ag metal layer. In addition, optimization and control of the thickness of the nano-scale Ag layer are important in obtaining highly transparent ZTO/Ag/ZTO electrodes, because antireflection is strongly influenced by Ag thickness. Moreover, IOSCs fabricated on optimized ZTO/Ag/ZTO electrodes with Ag thicknesses of 12 nm showed power conversion efficiencies (2.55%) comparable to that of an IOSC prepared on a crystalline ITO electrode (2.45%), due to the low sheet resistance and high optical transmittance in the range of 400-600 nm. The performances of ZTO/Ag/ZTO multilayer electrodes indicate that ZTO/Ag/ZTO multilayers are promising as indium-free, transparent electrode substitutes for conventional ITO electrodes in cost-efficient IOSCs.     

Influences of different TiO2 morphologies and solvents on the photovoltaic performance of dye-sensitized solar cells

The effects of TiO₂ photoelectrode's surface morphology and different solvents on the photovoltaic performance of dye-sensitized solar cells (DSSCs) were studied. By successive coating of TiO₂ suspension, composed of low and high molecular weight poly(ethylene)glycol (PEG) as a binder, double layered TiO₂ photoelectrodes with four different structures were obtained. Among the DSSCs with different TiO₂ electrodes, DSSC with P2P1 electrode (P2 and P1 correspond to PEG molecular weights of 20,000 and 200,000, respectively) showed higher performance under identical film thickness at a constant irradiation of 100 mW cm⁻², which may be correlated with large pore size and high surface area of the corresponding TiO₂ electrode. This was confirmed by electrochemical impedance spectroscopy (EIS) analysis of the DSSC and the transient photovoltage measurement of electrons in the TiO₂ electrode. Among the different solvents investigated here, the DSSC containing acetonitrile showed high conversion efficiency and the order of performance of the DSSCs with different solvents were AN > MPN > PC > GBL > DMA > DMF > DMSO. Better correlation was observed between the donor number of solvents and photoelectrochemical parameters of the DSSCs containing different solvents rather than the measured viscosity and dielectric constant of solvents. The reasons for the low performance of the DSSCs containing DMA, DMSO and DMF, respectively, were due to the negative shift of TiO₂ conduction band and the desorption of dye molecules from the TiO₂ photoelectrode by those solvents.     

Dye-sensitized solar cells based on natural and artificial phycobiliproteins to capture low light underwater

We developed dye-sensitized solar cells (DSSCs) based on natural and artificial phycobiliproteins (PBPs) to capture low light underwater. We assembled DSSCs with seven types of PBPs as sensitizers and studied their photoelectric properties. The results showed that the PBPs could markedly improve the photoelectrical properties of the DSSCs. The sensitization achieved by B-phycoerythrin (B-PE) from Porphyridium cruentum was superior to that of the other PBPs. The short-circuit current density, open circuit voltage, fill factor, and photoelectric conversion efficiency of the DSSC containing B-PE with a mesoporous titanium dioxide film as a photoelectrode were 3.236 mA/cm², 0.545 V, 0.569, and 1%, respectively. The DSSC based on B-PE displayed its highest photoelectric conversion efficiency between 525 and 570 nm. However, the maximum photoelectric conversion efficiencies of the DSSCs based on C-phycocyanin from Spirulina platensis and artificial PBPs were observed around 690 nm. DSSCs containing B-PE show great potential for use in underwater photovoltaic applications.     

Synthesis of new low band gap dyes with BF2-azopyrrole complex and their use for dye-sensitized solar cells

The diazonium salt derived from 4-aminobenzoic acid, 4-aminophenol or 2-aminophenol reacted with half equivalent of pyrrole to afford symmetrical 2,5-bisazopyrroles. They reacted subsequently with boron trifluoride in the presence of triethylamine to afford the corresponding BF₂-azopyrrole complexes D1, D2 and D3 respectively. They were soluble and stable in nonprotic solvents such as chloroform, dichloromethane and tetrahydrofuran but unstable in protic solvents such as ethanol. Their absorption spectra were broad with optical band gap of 1.49-1.70 eV. Among these dyes D2 displayed the broader absorption spectrum with low band gap of 1.49 eV. We have utilized these complexes as photosensitizers for quasi solid state dye-sensitized solar cells (DSSCs) and achieved power conversion efficiency in the range of 4.0-6.0%. We have also found that the co-adsorption of citric acid hindered the formation of dye aggregates and might improve the electron injection efficiency leading to an enhancement in short circuit photocurrent. This work suggests that metal-free dyes based on BF₂-azopyrrole complex are promising candidates for improvement of the DSSC performance.     

Nanocrystalline TiO2 film with textural channels: Exhibiting enhanced performance in quasi-solid/solid-state dye-sensitized solar cells

Novel nanocrystalline TiO₂ films with the textural channels are obtained for dye-sensitized solar cells (DSSCs). The textural channels consisting of the cracks on the surface and the nanopores with average diameter of about 41 nm are produced by packaging ZnO nanowires with diameter of 30–50 nm into TiO₂ films and subsequently etching ZnO nanowires by hydrochloric acid. The performances of DSSCs based on novel TiO₂ films (with the textural channels) and traditional TiO₂ films (without the textural channels) are investigated, respectively. When two kinds of typical quasi-solid-state electrolytes and one kind of solid-state electrolyte are used, the energy conversion efficiencies of DSSCs from novel TiO₂ films are improved by 20–30% compared to that from traditional TiO₂ films. The reasons for the great improvement are investigated chiefly by UV–vis absorption spectra, field emission-scanning electron microscope (FE-SEM) and electrochemical impedance spectroscopy (EIS) technique. The results show that the introduction of the textural channels facilitates better penetration of quasi-solid/solid-state electrolytes into the nanopores of novel TiO₂ films and thus results in better interfacial/electrical contact and faster interfacial reaction.     

Status and outlook of sensitizers/dyes used in dye sensitized solar cells (DSSC): a review

Dye‐sensitized solar cells (DSSCs) have become a topic of significant research in the last two decades because of their scientific importance in the area of energy conversion. Currently, DSSC is using inorganic ruthenium (Ru)‐based, metal‐free organic dyes, quantum‐dot sensitizer, perovskite‐based sensitizer, and natural dyes as sensitizer. The use of metal‐free, quantum‐dot sensitizer, perovskite‐based sensitizer, and natural dyes has become a viable alternative to expensive and rare Ru‐based dyes because of low cost, ease of preparation, easy attainability, and environmental friendliness. Most of the alternatives to Ru‐based dyes have so far proved inferior to the Ru‐based dyes because of their narrow absorption bands (Δλ ≈ 100–250 nm), adverse dye aggregation, and instability. This review highlights the recent research on sensitizers for DSSC, including ruthenium complexes, metal‐free organic dyes, quantum‐dot sensitizer, perovskite‐based sensitizer, mordant dyes, and natural dyes. It also details and tabulates all types of sensitizer with their corresponding efficiencies. Plot of progress in efficiency (η) of DSSC till date based on different types of sensitizers is also presented. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.     

Photovoltaic effect in arylenevinylene-co-pyrrolenevinylene (AVPV)

Arylenevinylene-co-pyrrolenevinylene (AVPV) is a promising candidate amongst the group of new photovoltaic materials. It is a low band gap organic material with a band gap of 1.84 eV and absorbs sunlight in 300-700 nm range. In this paper, we demonstrate the photovoltaic effect in an organic bulk heterojunction photovoltaic device based on the blend of AVPV as an electron donor and [6,6]-phenyl-C₆₁ butyric acid methyl ester (PCBM) as the acceptor. The short-circuit current density of the device was of the order of 0.55 μA cm⁻² with an open-circuit voltage of 0.7 V, measured under 1 sun illumination of AM 1.5 through a calibrated solar simulator. Fill factor was estimated to be 12%. Further, the tests conducted after 2 weeks showed that short-circuit current was 0.21 μA cm⁻² and open-circuit voltage was 0.5 V with a fill factor of 9.8%, suggesting the possibility of stable AVPV-based organic solar cell (OSC).     

Recent advancement in the performance of solar cells by incorporating transition metal dichalcogenides as counter electrode and photoabsorber

Two‐dimensional (2D) transition metal dichalcogenides (TMDCs) architectures have revealed fascinating characteristics such as direct band gap, strong light absorption, and novel electrochemical properties, which make them promising materials for photovoltaic applications. The review focuses on (1) the study of electrochemical and photovoltaic properties of TMDCs thereby using them as counter electrodes (CEs) in dye‐sensitized solar cells (DSSCs) and (2) analyzing the light absorption and charge transport performance of TMDCs heterostructures with different 3D materials. We have further investigated different materials in combination with TMDCs such as reduced graphene oxide nanocomposite, graphene flakes, and molybdenum as CEs in DSSCs. Conventionally, platinum (Pt) is used as a CE material for DSSCs that displays excellent catalytic activity and high electrical conductivity but due to the high cost and scarcity of Pt limits the large‐scale production. Therefore, the excellent electrochemical properties and cost‐effectiveness of TMDCs make them promising contender to replace Pt as CEs in DSSCs. Additionally, the photovoltaic properties of TMDCs and their heterostructures with various materials such as silicon, gallium arsenide, indium phosphate, tungsten disulfide, boron nitride, and organic polymers are reviewed. TMDCs are also investigated as hole transport layer (HTL) and electron transport layer (ETL) with various organic polymers such as P3HT, PCBM, PEDOT:PSS, PTB7, and spiro‐OmeTAD for organic and perovskite‐based solar cells (SCs). The utilization of TMDCs as CEs and photoabsorbers enhances the power conversion efficiency (PCE) to generate cost‐effective and high performance SC devices that can be exploit for future technological applications.     

Dye-sensitized nanocrystalline TiO2 solar cells based on novel coumarin dyes

We have developed dye-sensitized nanocrystalline TiO₂ solar cells (DSSCs) based on novel coumarin-dye photosensitizers. The absorption spectra of these novel dyes are red-shifted remarkably in the visible region relative to the spectrum of C343, a conventional coumarin dye. Introduction of a methine unit (–CH=CH–) connecting the cyano (–CN) and carboxyl (–COOH) groups into the coumarin framework expanded the π-conjugation in the dye and thus resulted in a wide absorption in the visible region. These novel dyes performed as efficient photosensitizers for DSSCs. A DSSC based on 2-cyano-5-(1,1,6,6-tetramethyl-10-oxo-2,3,5,6-tetrahydro-1H,4H,10H-11-oxa-3a-aza-benzo[de]anthracen-9-yl)-penta-2,4-dienoic acid (NKX-2311), produced a 6.0% solar energy-to-electricity conversion efficiency (η), the highest performance among DSSCs based on organic-dye photosensitizers, under AM 1.5 irradiation (100 mW cm^–2) with a short-circuit current density (J_sc) of 14.0 mA cm^–2, an open-circuit voltage (V_oc) of 0.60 V, and a fill factor of 0.71. Our results suggests that the structure of NKX-2311 whose carboxyl group is directly connected to the –CH=CH– unit, is advantageous for effective electron injection from the dye into the conduction band of TiO₂. In addition, the cyano group, owing to its strong electron-withdrawing ability, might play an important role in electron injection in addition to a red shift in the absorption region. On a long-term stability test under continuous irradiation with white light (80 mW cm^–2), stable performance was attained with a solar cell based on the NKX-2311 dye with a turnover number of 2.6×10⁷ per one molecule.     

On the photophysical and electrochemical studies of dye-sensitized solar cells with the new dye CYC-B1

In this study, the photoelectrochemical characteristics of a ruthenium photosensitizer with an alkyl bithiophene group, designated as CYC-B1, are studied. The effect of mesoporous TiO₂ film thickness on the photovoltaic performance of CYC-B1 and N3 dye-sensitized solar cells was investigated. The performance of the dye-sensitized nanocrystalline TiO₂ solar cells (DSSC) fabricated using CYC-B1 dye-anchored TiO₂ photoelectrode showed a convincing enhancement in cell efficiency when the TiO₂ film thickness was increased from 3 μm (eff.=5.41%) to 6 μm (eff.=7.19%). The efficiency of the CYC-B1-sensitized DSSC was maximum at 6 μm of the TiO₂ film thickness, reached its limiting value and remained constant up to 53 μm, although a similar trend was also observed for N3 dye-sensitized DSSC, however, the maximum efficiency achieved was only at 27 μm thickness (eff.=6.75%). As expected, the photocurrent density generated in the DSSC modified by CYC-B1 dye is larger than that from N3 dye. The effect of guanidinium thiocyanate (GuSCN) (additive) addition to the electrolyte on the photovoltaic performance of DSSCs based on CYC-B1 was also investigated. Furthermore, the electrochemical impedance spectroscopy (EIS) technique and photo-transient laser method have been employed to analyze the charge transfer resistances (R_ct) and the lifetime of the injected electrons on the TiO₂ containing different thicknesses.     

Silicon-organic pigment material hybrids for photovoltaic application

Hybrid materials of silicon and organic dyes have been investigated for possible application as photovoltaic material in thin film solar cells. High conversion efficiency is expected from the combination of the advantages of organic dyes for light absorption and those of silicon for charge carrier separation and transport. Low temperature remote hot wire chemical vapor deposition (HWCVD) was developed for microcrystalline silicon (μc-Si) deposition using SiH₄/H₂ mixtures. As model dyes zinc phthalocyanines have been evaporated from Knudsen type sources. Layers of dye on μc-Si and μc-Si on dye films, and composites of simultaneously and sequentially deposited Si and dye have been prepared and characterized. Raman, absorption, and photoemission spectroscopy prove the stability of the organic molecules against the rough HWCVD-Si process. Transient microwave conductivity (TRMC) indicates good electronic quality of the μc-Si matrix. Energy transfer from dye to Si is indicated indirectly by luminescence and directly by photoconductivity measurements. F_xZnPc pigments with x=0,4,8,16 have been synthesized, purified and adsorbed onto H-terminated Si(1 1 1) for electronic state line up determination by photoelectron spectroscopy. For x=4 and 8 the dye frontier orbitals line up symmetrically versus the Si energy gap offering similar energetic driving forces for electron and hole injection, which is considered optimum for bulk sensitization and indicates a direction to improve the optoelectronic coupling of the organic dyes to silicon.     

Photocatalytic overall water splitting with dual-bed system under visible light irradiation

Photocatalytic overall water splitting has been demonstrated with WO₃ for oxygen producing photocatalyst (OPC), and Rh-doped SrTiO₃ for hydrogen producing photocatalyst (HPC) in a simulated dual-bed system under visible light irradiation (λ ≥ 400 nm). The Fe³⁺/Fe²⁺ redox couple was chosen as the most effective electron mediator between OPC and HPC. The overall performance of the dual-bed system was limited by the low activity of HPC, and thus the activity of HPC should be increased to improve the overall performance. For overall water splitting reaction in a dual-bed system, the conduction band of OPC must be more negative than the redox potential of the electron acceptors and the valence band of HPC must be more positive than the redox potential of the electron donors.     

Effect of surface modification of TiO2 on the photovoltaic performance of the quasi solid state dye sensitized solar cells using a benzothiadiazole-based dye

We report the preparation of nanoporous TiO₂ electrode modified with an insulating material—BaCO₃ and used as electrode for quasi solid state dye sensitized solar cells (DSSCs), with a benzothiadiazole-based dye (BTDR2) as sensitizer and PEDOT:PSS coated FTO as counter electrode. We found that the BaCO₃ modification significantly increases the dye adsorption, resulting from the fact that the surface of BaCO₃ is more basic than TiO₂. The performance of the DSSCs with and without BaCO₃ modified TiO₂ electrodes were analyzed by cyclic voltammograms, optical absorption spectra, current-voltage characteristics in dark and under illumination and electrochemical impedance spectra. The photovoltaic performance has been significantly improved for the BaCO₃ modified electrode as compared to bare TiO₂ electrode having the same other components in the DSSCs. The value of the overall power conversion efficiency (η) improves from 2.42% to 4.38% under illumination intensity, when BaCO₃ modified electrode is used instead of bare TiO₂ electrode. The improvement in η has been attributed to the increased dye adsorption, reduction in recombination rate and enhancement in the electron lifetime when the modified TiO₂ electrode is used.     

Cubic titanium dioxide photoanode for dye-sensitized solar cells

Following from the recently evolved concept of significantly improving the photovoltaic efficiency in dye-sensitized solar cells (DSSCs) by reducing the loss of electrons on the spherical surface of titanium dioxide, this study examines the synthesis of cubic TiO₂ with a special morphology to overcome this electron loss and investigates its application to DSSCs. Cubic TiO₂ is synthesized by an advanced rapid hydrothermal method, with the addition of an amine species additive. Transmission electron microscopy (TEM) images confirm the cubic shape of the TiO₂ particles with a diameter less than 5-10 nm. Using N719 dye under illumination with 100 mW cm⁻² simulated sunlight, the application of cubic TiO₂ to DSSCs affords an energy conversion efficiency of approximately 9.77% (4.0-μm thick TiO₂ film), which is considerably enhanced compared with that achieved using a commercial, spherical TiO₂. Electrostatic force microscopy (EFM) and impedance analyses reveal that the electrons are transferred more rapidly to the surface of a cubic TiO₂ film than on a spherical TiO₂ film.     

Pomegranate leaves and mulberry fruit as natural sensitizers for dye-sensitized solar cells

This study employs chlorophyll extract from pomegranate leaf and anthocyanin extract from mulberry fruit as the natural dyes for a dye-sensitized solar cell (DSSC). A self-developed nanofluid synthesis system is employed to prepare TiO₂ nanofluid with an average particle size of 25 nm. Electrophoresis deposition was performed to deposit TiO₂ nanoparticles on the indium tin oxide (ITO) conductive glass, forming a TiO₂ thin film with the thickness of 11 μm. Furthermore, this TiO₂ thin film was sintered at 450 °C to enhance the thin film compactness. Sputtering was used to prepare counter electrode by depositing Pt thin film on FTO glass at a thickness of 20 nm. The electrodes, electrolyte (), and dyes were assembled into a cell module and illuminated by a light source simulating AM 1.5 with a light strength of 100 mW/cm² to measure the photoelectric conversion efficiency of the prepared DSSCs. According to experimental results, the conversion efficiency of the DSSCs prepared by chlorophyll dyes from pomegranate leaf extract is 0.597%, with open-circuit voltage (V_OC) of 0.56 V, short-circuit current density (J_SC) of 2.05 mA/cm², and fill factor (FF) of 0.52. The conversion efficiency of the DSSCs prepared by anthocyanin dyes from mulberry extract is 0.548%, with V_OC of 0.555 V and J_SC of 1.89 mA/cm² and FF of 0.53. The conversion efficiency is 0.722% for chlorophyll and anthocyanin as the dye mixture, with V_OC of 0.53 V, J_SC of 2.8 mA/cm², and FF of 0.49.     

Synthesis and characterization of trivalent metal porphyrin with NCS ligand for application in dye-sensitized solar cells

Two novel trivalent metal porphyrin dyes, P_Mn-HT-SCN and P_Ga-HT-SCN, were designed, synthesized and firstly applied in dye-sensitized solar cells (DSSCs). These two dyes possess porphyrin donor modified with manganese (III) and gallium (III) as coordination metal and NCS as the second ligand, cyanoacrylic acid as electron-accepting moiety and 4-hexylthiophene as π-spacers. Each of the porphyrin showed different adsorption behavior and saturated coverage on the TiO₂ surface. Between the two dyes, the P_Mn-HT-SCN-based DSSCs afforded the best photovoltaic performance: a short-circuit photocurrent density (J_sc) of 4.32 mA/cm², an open-circuit photovoltage (V_oc) of 0.61 V and a fill factor (FF) of 0.58, corresponding to a solar-to-electricity conversion efficiency of 1.53% under 100 mW/cm² irradiation.     

Novel iminocoumarin dyes as photosensitizers for dye-sensitized solar cell

Novel iminocoumarin dyes (2a-c and 3a-c) having carboxyl and hydroxyl anchoring groups onto the dyes skeletons have been designed and synthesized for the application of dye-sensitized nanocrystalline TiO₂ solar cells (DSSCs). The photophysical and electrochemical studies showed that these iminocoumarin dyes are suitable as light harvesting sensitizers in DSSC application. The dyes having carboxyl and hydroxyl anchoring groups (2a-c) showed better efficiency when compared to the dyes having carboxyl group (3a-c) alone. The cell consisted of dye 2a generated the highest solar-to-electricity conversion efficiency (η) of 0.767% (open circuit voltage (V_oc) = 0.491 V, short circuit photocurrent density (J_sc) = 2.461 mA cm⁻², fill factor (ff) = 0.635) under simulated AM 1.5 irradiation (1000 W m⁻²) with a total semiconductor area of 0.25 cm². The corresponding incident photon-to-current conversion efficiency (IPCE) of the above cell was 21.38%. The overall low efficiency of the dyes is ascribed to the lack of light harvesting ability at longer wavelength region.