Dye-based Dye-sensitized Solar Cells Research Articles

Squaric Acid Core Substituted Unsymmetrical Squaraine Dyes for Dye-Sensitized Solar Cells: Effect of Electron Acceptors on Their Photovoltaic Performance

The design and development of sensitizing dyes possessing wide-wavelength photon harvesting encompassing visible to near-infrared (NIR) wavelength regions are unavoidable for increasing the overall efficiency of dye-sensitized solar cells (DSSCs). In this study, three far-red-sensitive squaraine sensitizers were designed computationally, synthesized, and characterized, aiming towards their suitability as a potential sensitizer for DSSCs. It has been found that the incorporation of an electron acceptor moiety in the central squaraine core brought about a red shift in the absorption maximum (λmax) and the emergence of a secondary absorption band in the blue region, thus broadening the photon-harvesting window. In addition, it also lowered the dye’s HOMO energy level enabling a facile regeneration of the photo-excited dye, which improved the photovoltaic performance of SQ-223, exhibiting a photoconversion efficiency (PCE) of 4.67%. Thereafter, to address the issue of wide-wavelength photon harvesting, DSSCs were fabricated by co-adsorbing two complementary dyes SQ-223 and D-131 in various molar ratios. The DSSC fabricated with D-131 and SQ-223 in 9:1 molar ratio displayed the best photovoltaic performance with a PCE of 5.81%, a significantly higher PCE when compared to corresponding individual dye-based DSSCs containing D-131 (3.94%) and SQ-223 (4.67%).

Synergistic Effect of Size-Tailored Structural Engineering and Postinterface Modification for Highly Efficient and Stable Dye-Sensitized Solar Cells.

Despite significant progress in device performance, dye-sensitized solar cells (DSSCs) continue to fall short of their theoretical potential. Moreover, research in recent years needs to pay more attention to improving the device fabrication process. To achieve the theoretical efficiency limit, it is crucial to optimize the interface between the dye and TiO2 nanoparticles in the entire device stack. Our study indicates that optimizing the structure or size of the coadsorbents and implementing a monolayer adsorption process can be an effective strategy to reduce charge recombination and enhance light-harvesting properties. Our research aims to develop a surface-coating adsorbent plan that controls the TiO2 nanoparticle interface to achieve the radiative limit of power conversion efficiency (PCE). Specifically, we utilized 2-thiophenecarboxylic acid (THCA) or chenodeoxycholic acid (CDCA) as postinterfacial surface-coating adsorbents. Our results demonstrate that this approach effectively achieves the desired PCE limit. Combined with the coadsorbent structure engineering and interface optimization, the device increased the packing area on the TiO2 nanoparticles' surface, reaching an improved PCE of over 13.17% under simulated sunlight (1.5G), which is the highest efficiency of a porphyrin single dye-based DSSC. In particular, this practical approach was also applied to a large-area DSSC with an area of 3 cm2, yielding a remarkable PCE of 9.04%. Furthermore, when applied to a polymer gel electrolyte, this novel approach recorded the highest PCE of 11.16% with a long-term operational stability of up to 1000 h for the quasi-solid-state DSSCs. Our research findings provide a promising avenue for achieving high-performance DSSCs with ease of access and demonstrate practical applications as alternatives to conventional power sources.

Boosting the Efficiency of Dye-Sensitized Solar Cells by a Multifunctional Composite Photoanode to 14.13.

We report a new strategy to fabricate a multifunctional composite photoanode containing TiO2 hollow spheres (TiO2-HSs), Au nanoparticles (AuNPs) and novel NaYF4:Yb,Er@NaLuF4:Eu@SiO2 upconversion nanoparticles (UCNPs). The AuNPs are grown on the photoanode film including TiO2-HSs and UCNPs by a simple in-situ plasmonic treatment. As a result, an impressive power conversion efficiency of 14.13% is obtained, which is a record for N719 dye-based dye-sensitized solar cells, demonstrating great potential for the solar cells toward commercialization. This obvious enhancement is ascribed to a collaborative mechanism of the TiO2-HSs exhibiting excellent light-scattering ability, of the UCNPs converting near-infrared photons into visible photons and of the AuNPs presenting outstanding surface plasmon resonance effect. Notably, a steady-state experiment further reveals that the champion cell exhibits 95.33% retainment in efficiency even after 180 h of measurements, showing good device stability.

Butea monosperma, crown of thorns, red lantana camara and royal poinciana flowers extract as natural dyes for dye sensitized solar cells with improved efficiency

The cost-effective and eco-friendly natural dyes are sustainable alternatives to synthetically prepared ruthenium-based dyes. This study aims to explore the effect of natural dyes extracted from four different flowers on improving solar cell efficiency. The natural dyes are extracted from butea monosperma (BM), crown of thorns (CT), red lantana camara (RL) and royal poinciana flowers (RP). The dye-sensitized solar cells (DSSCs) were constructed using TiO2 nanorods (NRs) and light-harvesting natural dyes. Highly ordered and vertically oriented TiO2 NRs arrays were synthesized on FTO substrate and used as photoanode to fabricate natural dye based DSSCs. TiO2 NRs facilitate the infiltration of the liquid-state electrolyte and good binding with dye molecules; their one-dimensional structural feature provides effective charge transport. A significant improvement in the photo conversion efficiency (PCE) of TiO2 NRs sensitized and light-harvesting natural dye-based DSSCs has been observed. The structural, morphological, and optical properties of the TiO2 photoanode as well as the optical properties of the extracted dyes were studied using characterization techniques. The PCE of DSSCs based on natural dye extracts from BM, CT, RL and RP flowers were observed to be 2.89%, 1.20%, 1.02% and 0.72%, respectively. This work reports the highest PCE (2.89%) to date for DSSC fabricated using BM flower-based natural dyes; therefore, it can be a sustainable alternative to synthetic dyes.

Open-Circuit Voltage Degradation by Dye Mulliken Electronegativity in Multi-Anchor Organic Dye-Based Dye-Sensitized Solar Cells

Open-Circuit Voltage Degradation by Dye Mulliken Electronegativity in Multi-Anchor Organic Dye-Based Dye-Sensitized Solar Cells

Fabrication of eco-friendly, low-cost dye sensitized solar cells using harda fruit-based natural dye

The dye-sensitized solar cells (DSSCs) have been eyed as a potential alternative to the expensive silicon-based solar cells. However, most high-performing DSSCs employ ruthenium (Ru) bipyridyl derivatives dye as a photosensitizer, which is costly and toxic. In this research, low-cost eco-friendly alternative dye materials, namely harda fruit-based natural dye and direct dye (fabric dye) were investigated for application in the DSSCs. Field emission scanning electron microscopy, Raman, and X-ray diffraction studies have been performed to gain insight into morphological, structural, and crystalline properties of photosensitizers. The DSSCs based on the natural dye and fabric dye was successfully demonstrated with 3.52% and 0.80% efficiency, respectively. The analysis of photovoltaic parameters reveals that the superior performance of a natural dye-based DSSC results from the better morphological and crystalline properties of the natural dye-based sensitizers. The decent performance shown by a natural dye-based DSSC in the work is expected to propel the research in the area of natural dye-based DSSCs.

Enhanced performance of dye-sensitized solar cells by co-sensitization of metal-complex and organic dye

We systematically investigated a co-sensitized dye comprising of the Ru-complex (N719) dye blended with organic (Coomassie brilliant-blue R-250) as a novel photosensitizer for application in dye-sensitized solar cells (DSSCs). Compared with DSSCs made with the individual dyes, the power conversion efficiency of DSSC with co-sensitized dye is increased by 22 %, i.e., from 9.07 to 11 %. This enhancement results mainly from the significant increase in the open-circuit voltage (VOC) upon co-sensitization due to the upward movement of the conduction band edge and reduction in the charge recombination. Impedance spectroscopy analysis reveals higher charge recombination resistance and greater carrier lifetime for the co-sensitized dye-based DSSC, suggesting that the suppressed recombination due to improved morphology and reduced defects yields a high VOC. Moreover, co-sensitized DSSC exhibited enhanced short circuit current (JSC) and fill factor (FF). This strategy of using a co-sensitized dye as a photosensitizer in DSSCs could pave an effective way to approach high-performance, cost-effective DSSCs.

Correlation Study on Biopolymer-Blended Cobalt and Iodine Gel Electrolytes to Enhance the Efficiency of Natural Dye-Based DSSCs

In this study, we prepared a new natural sensitizer from blood berry extract (BB dye) and coupled it with a series of biopolymer gel electrolytes consisting of Co2+/3+ or I–/I3–, such as GE 1, GE 2, GE 3, GE 4, GE 5, and GE 6. An as-prepared natural dye was characterized via UV–visible spectroscopy to confirm the behavior of the dye, which showed an absorption range at 484 nm. The interaction between the TiO2 surface and the BB dye was analyzed by density functional theory (DFT) studies. All six biogel electrolytes were characterized using Fourier transform infrared (FTIR), UV, X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and cyclic voltammetry (CV) techniques to validate the integration of redox mediators into polymer hosts. The bioelectrolytes GE 1, GE 2, GE 4, and GE 5 contain a single polymer matrix (xanthan gum or gelatin) and showed a very low photo-conversion efficiency. At the same time, GE 3 and GE 6 contain a blended polymer matrix (xanthan gum and gelatin) and achieved a higher power conversion efficiency (PCE) of 0.86 and 2.06%, respectively, under 1 sun illumination. The redox mediator Co2+/3+ or I–/I3– incorporated into both single and blended polymer matrixes played a vital role in regenerating the BB dye. In this case, the bioblended polymer gel electrolyte (GE 6) consisting of a Co2+/3+ redox pair attained a high conductivity of 5.97 × 10–5 S/cm–1 and a chemical capacitance of 15.02 ×10–6 F compared to the I–/I3–-incorporated electrolyte. The PCE reports were sustained by the electrochemical impedance spectrum results such as a larger charge at the Pt/electrolyte interface, a lower charge transfer resistance at the TiO2/dye/electrolyte interface, and a higher chemical capacitance. The introduction of a biopolymer cobalt redox-based gel electrolyte with the natural BB dye improves the electron lifetime and readily reduces the recombination reaction. The integration of a natural dye with a blended biopolymer gel electrolyte can pave the way to generate new eco-friendly dye-sensitized solar cells (DSSCs) with high stability.

Effect of 1-Substituted 2-(Pyridin-2-yl)-1H-Benzo[d]imidazole Ligand-Coordinated Copper and Cobalt Complex Redox Electrolytes on Performance of Ru(II) Dye-Based Dye-Sensitized Solar Cells

A comparative study has been attempted on 1-substituted 2-(pyridin-2-yl)-1H-benzo[d]imidazole ligand-coordinated copper and cobalt metal complex electrolytes Cu+/2+[nbpbi]2(PF6-)1/2, Cu+/2+[npbi]2(PF6-)1/2, Co2+/3+[nbpbi]3(PF6-)2/3, and Co2+/3+[npbi]3(PF6-)2/3 in dry acetonitrile coupled with both N3 and N719 dyes in dye-sensitized solar cell (DSSC) devices. Impressively, the copper metal sites coordinated with ligands nbpbi (L1) and npbi (L2) shift the redox potential about 190-200 mV and pave the way to achieve remarkably higher power current efficiency, which is clarified with cyclic voltammetry, electrochemical impedance spectrum, electron lifetime, and quasi Fermi-level experimental results. Overall efficiencies of 4.99, 4.82, 3.26, and 3.19% under 1 sun conditions (100 mW cm-2) were obtained for Cu+/2+[nbpbi]2(PF6-)1/2 and Cu+/2+[npbi]2(PF6-)1/2 electrolytes coupled with the sensitizers (N3 and N719 dyes), which are considerably higher than those acquired for devices containing the cobalt electrolytes. These results signify a record for copper complex-based electrolytes coupled with ruthenium dyes in liquid DSSCs. In particular, bulky acceptor 4-nitro benzyl moiety-substituted 2-(pyridin-2-yl)-benzimidazole (on the N-H position) (ligand L1)-coordinated copper metal complex electrolytes achieved higher efficiency, approaching a suitable redox potential of 0.68 V versus NHE. At the same time, the napthyl moiety-substituted 2-(pyridin-2-yl)-benzimidazole (ligand L2)-coordinated copper metal complex electrolytes showed less redox potential due to its donating nature. It was determined that the Jsc and PCE increment of the devices consisting of Cu+/2+[nbpbi]2(PF6-)1/2 electrolytes was mainly attributed to various factors such as higher chemical capacitance, larger charge, longer electron life time, a downward shift in the quasi Fermi level of TiO2, the slow recombination process, and fast dye regeneration. These results make easily tunable metal complexes bearing a new sort of 1-substituted 2-(pyridin-2-yl)-1H-benzo[d]imidazole ligand-based electrolytes as very promising copper electrolytes for further improvements of extremely efficient liquid DSSCs.

Dye extracted from Costus woodsonii leave as a natural sensitizer for dye-sensitized solar cell

Current work employs dye extracted from leaves of Costus woodsonii as a new sensitizer for dye-sensitized solar cells (DSSCs). The leave was extracted in three different solvents namely ethanol, methanol, and acetone. Extraction of leaves was carried out by the freezing method. DSSCs with the configuration of TiO2/dye/electrolyte/Pt were assembled. The dyes in DSSCs were Costus woodsonii leaves extracted in methanol, ethanol, and acetone. DSSC with methanol extract of leaves has an efficiency of 0.23 % and short-circuit current density (Jsc) of 0.63 mA cm-2. DSSC sensitized with ethanol extract of leaves has an efficiency of 0.37 % and Jsc of 0.85 mA cm-2. DSSC sensitized with acetone extract of leaves shows the highest efficiency of 0.48 % and Jsc of 1.35 mA cm-2. The performance of the DSSCs in this work is compared with other natural dye-based DSSCs. The efficiency obtained in this work is better or at par with the works reported by other researchers.
 Keywords: Natural dye; Costus woodsonii; Leave; Dye-sensitized solar cells

Study on combination of natural red and green dyes to improve the power conversion efficiency of dye sensitized solar cells

In this paper, natural red dye extracted from beetroot (Beta vulgaris) and green dye extracted from spinach (Spinacia oleracea) was used as a sensitizer source for natural dye-based dye-sensitized solar cells (DSSC). DSSC, sensitized with natural red and green dyes yields low cell performance, i.e, for red dye efficiency obtained was, η= 0.56% and for green dye, η= 0.49%. Here to improve the cell performance, these two dyes (red and green) were combined at different volume ratios in order to get the maximum cell efficiency and the optimum dye combination ratio. From the UV absorption spectrum, the combination of dyes showed a wide absorption spectra and higher absorbance in the visible solar spectrum than both the single individual red or green dye. By the optimized combination of dyes (80% red + 20% green) co-sensitized DSSC, the observed cell parameters were, Isc= 4.65 mA, Voc= 386.7mA and FF= 0.55. DSSC co-sensitized with the optimum combination of red and green dyes, the maximum cell efficiency obtained was 0.99%, which is almost 2 and 1.77 times higher than that of the single individual red and green dyes.

Highly efficient organic indolocarbazole dye in different acceptor units for optoelectronic applications—a first principle study

A series of novel organic dyes (ICZA1, ICZA2, ICZA3, ICZA4) with D-π-A structural configuration incorporating indolo[3,2,1-jk]carbazole moiety as donor (D) unit, thiophene as π-linker and 2-cyanoacrylic acid as acceptor unit were investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. Indolo[3,2,1-jk]carbazole-based D-π-A dyes composed of different acceptor groups were designed. By modulating acceptor unit, the efficiency of D-π-A dye-based dye-sensitized solar cells (DSSCs) can be further improved. In the present work, four novel push-pull organic dyes only differing in electron acceptor, have been designed based on the experimental literature value of IC-2. In order to further improve the light harvesting capability of indolo[3,2,1-jk]carbazole dyes, the acceptor influence on the dye performance were examined. The NLO property of the designed dye molecules can be derived as polarizability and hyperpolarizability. The calculated value of ICZA2 dye is the best candidate for NLO properties. Furthermore, the designed organic dyes exhibit good photovoltaic performance of charge transfer characteristics, driving force of electron injection, dye regeneration, global reactivity, and light harvesting efficiency (LHE). From the calculated value of ICZA4 dye, it has been identified as a good candidate for DSSCs applications. Finally, it is concluded that the both ICZA2 and ICZA4 dyes theoretically agrees well with the experimental value of IC-2 dye. Hence, the dyes ICZA2 and ICZA4 can serve as an excellent electron withdrawing groups for NLO and DSSCs applications.

IMPROVING STABILITY OF CHLOROPHYLL AS NATURAL DYE FOR DYE-SENSITIZED SOLAR CELLS

Natural dyes have attracted much researcher’s attention due to their low-cost production, simple synthesis processes and high natural abundance. However the dye-sensitized solar cells (DSSCs) based natural dyes have higher tendency to degradation. This article reports on the enhancement of performance and stability of dye-sensitized solar cells (DSSCs) using natural dyes. The natural dyes were extracted from papaya leaves by ethanol solvent at a temperature of 50 °C. Then the extracted dyes were isolated and modified into Mg-chlorophyll using column chromatography. Mg-chlorophyll was then synthesized into Fe-chlorophyll to improve stability. The natural dyes were characterized using ultraviolet-visible spectrometry, Fourier transform infrared spectroscopy, and cyclic voltammetry. The performance of DSSCs was tested using a solar simulator. The results showed the open-circuit voltage, the short-circuit current density, and the efficiency of the extracted papaya leaves-based DSSCs to be 325 mV, 0.36 mA/cm2, and 0.07%, respectively. Furthermore, the DSSCs with purified chlorophyll provide high open-circuit voltage of 425 mV and short-circuit current density of 0.45 mA/cm2. The use of Fe-chlorophyll for sensitizing the DSSCs increases the efficiency up to 2.5 times and the stability up to two times. The DSSCs with Fe-chlorophyll dyes provide open-circuit voltage, short-circuit current density, and efficiency of 500 mV, 0.62 mA/cm2, and 0.16%, respectively. Further studies to improve the current density and stability of natural dye-based DSSCs along with an improvement in the anchor between dyes and semiconducting layers are required.

Influence of Poly(N-vinylcarbazole) as a Photoanode Component in Enhancing the Performance of a Dye-Sensitized Solar Cell

Increasing the dye adsorption and minimization of charge recombination are pivotal in improving the efficiency of a dye-sensitized solar cells (DSSCs). In the present investigation, these two effects have been accomplished through the introduction of poly(N-vinylcarbazole) (PVK) as an auxiliary component of the TiO2 photoanode in a N719 dye-based DSSC. TiO2/PVK hybrid nanocomposites were prepared by simple blending of TiO2 with small quantities of PVK (0.3–1.3 wt %) in the presence of PEG20000, acetylacetone, and Triton X-100. X-ray diffraction data revealed that the crystalline properties of TiO2 were not altered by the presence of PVK. The porosity and surface roughness of TiO2 were enhanced by the addition of PVK. Spin-coated TiO2–PVK nanocomposite films showed highly enhanced dye adsorption in comparison to pristine TIO2 films which had been attributed to an increase in the basicity of the TiO2 surface. The N719 dye-sensitized TiO2/PVK photoanodes were assessed for their performance in a DSSC assembled with the I–/I3– redox electrolyte and sputtered Pt as counter electrode. The quantity of PVK in the nanocomposite was optimized by evaluating the photovoltaic performance. A maximum power conversion efficiency of 7.10% was achieved with a 0.9 wt % PVK loaded TiO2, which was 58% greater than that of the pristine TiO2 cell (4.48%). Impedance data showed a very low charge-transfer resistance of 3.79 Ω and a high electron lifetime of 31.41 ms, implying an effective reduction in the back electron transfer.

Stability and efficiency of dye-sensitized solar cells based on papaya-leaf dye

The present article reports on the enhancement of the performance and stability of natural dye-based dye-sensitized solar cells (DSSCs). Natural dyes extracted from papaya leaves (PL) were investigated as sensitizers in TiO2-based DSSCs and evaluated in comparison with N719 dye. The acidity of the papaya-leaf extract dyes was tuned by adding benzoic acid. The TiO2 film-coated fluorine-doped tin oxide glass substrates were prepared using the doctor-blade method, followed by sintering at 450°C. The counter electrode was coated by chemically deposited catalytic platinum. The working electrodes were immersed in N719 dye and papaya dye solutions with concentrations of 8g/100mL. The absorbance spectra of the dyes were obtained by ultra-violet–visible spectroscopy. The energy levels of the dyes were measured by the method of cyclic voltammetry. In addition, Fourier transform infrared spectroscopy was used to determine the characteristic functionalities of the dye molecules. The DSSC based on the N719 dye displayed a highest efficiency of 0.87% whereas those based on papaya-leaf dye achieved 0.28% at pH 3.5. The observed improved efficiency of the latter was attributed to the increased current density value. Furthermore, the DSSCs based on papaya-leaf dye with pH 3.5–4 exhibited better stability than those based on N719 dye. However, further studies are required to improve the current density and stability of natural dye-based DSSCs, including the investigation of alternative dye extraction routes, such as isolating the pure chlorophyll from papaya leaves and stabilizing it.

Degradation of Cyanoacrylic Acid‐Based Organic Sensitizers in Dye‐Sensitized Solar Cells

Organic dyes have become widely used in dye-sensitized solar cells (DSSCs) because of their good performance, flexible structural modifications, and low costs. To increase the photostability of organic dye-based DSSCs, we conducted a full study on the degradation mechanism of cyanoacrylic acid-based organic sensitizers in DSSCs. The results showed that with the synergy between water and UV light, the sensitizer could desorb from the TiO2 surface and the cyanoacrylic acid unit of the sensitizer was transformed into the aldehyde group. It was also observed that the water content had a great effect on the degradation process. Our experiments conducted using (18) O-labeled water demonstrated that the oxygen atom of the aldehyde group identified in the degraded dye came from the solvent water in the DSSCs. Therefore, controlling the water content during DSSC fabrication, good sealing of cells, and filtering the UV light are crucial to produce DSSCs that are more durable and robust.

Effects of cation composition in the electrolyte on the efficiency improvement of black dye-based dye-sensitized solar cells

The effects of the addition of the tetrabutylammonium cation in the electrolyte on the performance of a black dye-based dye-sensitized solar cell (DSC) have been investigated. The conversion efficiency of the cosensitized DSC with black dye and D131 was improved to 11.8% by using an electrolyte containing three kinds of cations.

Thiophene-Bridged Double D-π-A Dye for Efficient Dye-Sensitized Solar Cell

An organic dye containing two D-π-A branches linked with a thiophene unit has been designed and synthesized for efficient dye-sensitized solar cells (DSSCs). As compared to the rod-shape of the single D-π-A analogue dye, the cross shape of the double D-π-A branched dye is favorable for reducing intermolecular interaction and retarding charge recombination. Controlled intensity modulated photovoltage spectroscopy reveals that electron lifetime for the double D-π-A dye-based DSSC is 14-fold longer than that for the corresponding single D-π-A dye-based DSSC. Linking two D-π-A branches with a thiophene unit increases open-circuit photovoltage by 100 mV and short-circuit photocurrent by 4.10 mA cm–2. As a consequence, power conversion efficiency is enhanced by about 2-fold. This work presents a new route to designing sensitizers with high suppression ability of charge recombination toward high-performance DSSCs.

Synthesis of Alkyl-functionalized Organic Dyes and Their Application to Dye Sensitized Solar Cells (DSSCs)

Department of Chemistry, Konkuk University, Seoul 143-701, KoreaReceived August 28, 2011, Accepted November 2, 2011Key Words : Dye-Sensitized Solar Cells (DSSCs), Bulky spacer, Photon to current conversion efficiencyRuthenium dye-based dye-sensitized solar cells (DSSCs)have received great deal of attraction from chemists andmaterial scientists because of their over 10% of photon tocurrent conversion efficiency.