Photovoltaic Performance Of Dye-sensitized Solar Cells Research Articles

Enhanced photovoltaic performance of dye sensitized solar cells using cesium bromide modified TiO2 electron transport layer

TiO2 is one of the most widely explored materials as an electron transport layer (ETL) in dye sensitized solar cells (DSSCs) due to its excellent physical and chemical properties. However, recombination at the device's interface slackens the charge carrier movement, adversely affecting their device performance. Rapid extraction of photogenerated charge carriers plays a vital role in developing high efficiency DSSCs. The conduction band alignment of TiO2 ETL and N719 dye light absorber plays a crucial role in charge carrier dynamics of DSSCs. Herein, the band structure of TiO2 ETL is finely tuned by the incorporation of cesium bromide (CsBr). At the optimal concentration (0.4 Wt. %), DSSCs achieved the best power conversion efficiency (PCE) of 9.28 % compared to 7.61 % for pristine TiO2. The modified TiO2–CsBr ETL induced a negative shift in flat band potential (Vfb) from −0.46 to −0.50 V, which improved the open circuit voltage (VOC), its work function (ɸ) from −4.71 to −3.75 eV and increased conduction band minimum (CBM) from −3.58 to −2.42 eV. CsBr incorporation increased electron density in TiO2 matrix, indicating the suppression of trap state and significantly improved the overall photovoltaic performance of DSSCs.

Double Fence Porphyrins Featuring Indacenodithiophene Group as an Effective Donor for High‐Efficiency Dye‐Sensitized Solar Cells

AbstractPorphyrins are an important category of dyes for efficient dye‐sensitized solar cells (DSSCs). However, the efficiency improvement of DSSCs lags behind those of organic and perovskite solar cells owing to deficiencies in new design strategies of dye molecular structures. Recently, double fence porphyrins with superior photovoltaic performance were reported, in which eight alkoxyl chains were introduced to wrap the porphyrin core and retard the approach of the electrolyte to the surface of TiO2. On the basis of the design strategy of double fence porphyrins, novel porphyrins bJS8, YS2, YS3, YS7, and MC1 featuring dual functional indacenodithiophene group are synthesized and their photovoltaic performance in DSSCs are studied. Among these new double fence porphyrin dyes, YS7 exhibits an improved power conversion efficiency of 11.4% (short circuit photocurrent (JSC) = 17.34 mA cm−2, open circuit photovoltage (VOC) = 0.864 V, and fill factor (FF) = 0.758) compared to the previously reported double fence porphyrin bJS2 of 10.7% (JSC = 16.59 mA cm−2, VOC = 0.849 V, and FF = 0.759) and the benchmark porphyrin dye GY50 of 10.1% (JSC = 16.14 mA cm−2, VOC = 0.863 V, and FF = 0.725) under optimized conditions, providing a new molecular design strategy for high‐efficiency porphyrin dyes in DSSCs.

Probing novel photoanodes relying on CuBiSe/metal' oxides nanocomposites-based dye-sensitizing solar cells

CuBiSe / Metal oxides (TiO2, V2O5, and ZnO) nanocomposites were synthesized by a simple and low-cost hydrothermal technique for application in Dye-Sensitised Solar Cells (DSSCs). XRD, XPS, SEM with EDX analysis, FTIR spectrum, UV visible Spectroscopy, PL spectrum, Hall Effect analysis, and Impedance analysis were performed to evaluate the prepared nanocomposites. The photovoltaic performance of DSSCs which were constructed with CBS/ TiO2, CBS/V2O5, and CBS/ZnO photoanodes were investigated. With a short-circuit, photocurrent density of 3.728 mA cm2, an open circuit voltage of 0.398 V, a fill factor of 0.72, and a Power conversion efficiency (PCE) of 1.07% was achieved for CBS/V2O5 DSSCs device, which is greater than that of DSSCs devices using CBS/ TiO2 and CBS/ZnO based photo-anodes (PCE = 0.62, and 0.37%). The obtained results propose that the prepared nanocomposite is an appropriate photo-anodic material for DSSCs applications.

Photovoltaic Properties of the Titanium Dioxide Compact Layer and Reduced Graphene Oxide for Dye-Sensitized Solar Cells Under Different Light Intensities

Dye-sensitized solar cells (DSSCs) demonstrate excellent performance under low-light conditions. In this current study, an investigation into the DSSCs photovoltaic performance under different light densities was conducted. The photoanode was made with spin coating and doctor blade methods. The photovoltaic efficiency increased when the titanium tetrachloride (TiCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) treatment and reduced graphene oxide (rGO) were introduced into the photoanode. The photoanode pretreatment and posttreatment of the TiCl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> process could effectively inhibit the recombination of the photogenerated electrons with the oxidized redox ions. The rGO could enhance the electron transport and so decrease the dark reaction. The photoelectric conversion efficiency (PCE) increased from 4.74% to 6.28% under 100 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The device achieved the optimal PCE at 10 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 8.78%.

Replacement for platinum in dye sensitized solar cell

In Dye-Sensitized Solar Cells (DSSC), the platinum -free counter electrode has its own charm. Copper selenide and lead sulphide thin films are tried as substitutes for the platinum electrode in this work. These materials were prepared by the Chemical Bath Deposition technique (CBD) and their structural, compositional and electrical properties were studied in detail. DSSC was fabricated using natural dye from pomegranate as the photosensitizer. The photovoltaic performance of DSSC was evaluated with the two alternate counter electrodes and compared with the conventional platinum electrode. Results show that DSSC using copper selenide electrode exhibits appreciable power conversion efficiency when compared to platinum electrode under similar conditions.

Remarkable 8.3% efficiency and extended electron lifetime towards highly stable semi-transparent iodine-free DSSCs by mitigating the in-situ triiodide generation

Achieving highly stable and efficient dye-sensitized solar cells (DSSCs) remains a major challenge for future industrial development. In the present work, a series of ionic conductors, such as ionic liquids (ILs), polysiloxane-based poly(ionic liquid)s (PILs), and their blends are employed as electrolytes in quasi-solid-state DSSCs. In particular, we study the effect of PILs ionic functionality interaction with the ILs and ethylene carbonate (EC) on the photovoltaic performance of DSSCs with and without iodine (I2). Omitting I2 from the electrolytes in fabricated DSSCs enhances both Voc and Jsc due to the reduced charge recombination and extended effective electron lifetime. We confirm through Raman spectroscopy that in I2-free DSSCs, the in-situ generated tri-iodides (I3−) ions are sufficient enough to complete the reaction mechanism. Additionally, the I2-free DSSCs exhibit enhanced transparency, encouraging our efforts towards BIPV suitable applications. When plasticized with EC, the ionic conductivities of the highly functionalized I2-free PIL-based DSSCs exceeds 10−3 S cm−1 at 30 °C, giving record PCE of 8.3% and 9.1% under standard (1 sun) and modest (0.3 sun) illumination, respectively. These devices also show excellent long-term stability, retaining about 84% of their initial efficiency after 26 months.

Improved performance of dye sensitized solar cell by exploration of photoanode and ruthenium based dye

We report two different fabrication methods (Doctors blade and Screen print) of photoanode and influence of three ruthenium based dyes (N3, N749 and Z907 and also their mixed dye) on dye sensitized solar cells (DSSCs). We found the increased effective surface area and lower densification in screen printed film. Rough surface of these films also improved adsorption of dyes to the photo anode film. On the other hand, mixed dye is an approach to harvest a wider range of solar lights on cells and exhibited peaks were found at 530 nm for N3 and 540 nm for Z907. Another peak at 620 nm was observed for N749 which revealed significant light absorption and photosensitization compared with the individual dye solutions. In this article, photovoltaic performances of DSSCs using these dyes and photoanodes were also evaluated and compared. The overall power conversion efficiencies of DSSCs lay in the range of 1.26–1.61%. Screen printed film with mixed dye showed the highest efficiency.

Quantum chemical and photovoltaic modeling of D-π-A organic dyes based on substituted arylamine electron donors in dye sensitized solar cells

In the present research, we designed four tunable triphenylamine (TPA) based organic dyes by applying various aminated electron donor groups and screened their electron donating effects on the electronic, optical and photovoltaic properties of the dyes for application in dye sensitized solar cells (DSSCs). In this respect, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) approaches were applied to investigate the enhanced electron donating effect of substituted TPA dyes on the strength of conjugation with thiophene and a C–C triple bond in the π-spacer fragment that led to a considerable effect on absorption properties, light harvesting efficiency and panchromatic sensitization of the designed dyes in DSSCs. In fact, since the most significant impediment of TPA-based organic dyes for high photovoltaic performance in DSSCs is their low absorption in the near-infrared spectrum, we aimed our modeling to introduce molecular dyes with reduced frontier molecular orbital energy gaps and hence, the favoured red-shift absorption spectra. Moreover, we have computationally concentrated on the photovoltaic performance of our novel dyes in DSSCs and demonstrated that employing aminated electron donating groups in TPA based organic dyes notably tunes the electron injection and regeneration driving forces and hence leads to higher power conversion efficiencies.

Isomeric tetrazole-based organic dyes for dye-sensitized solar cells: Structure-property relationships

Two new organic dyes (SD-1 and SD-2) featured with donor–π–acceptor architecture were synthesized and applied to dye-sensitized solar cells (DSSCs). In these sensitizers, an azo bridge π-spacer is used to link the phenyl tetrazole acceptor with 2-naphthol donors. To amplify the pull-push effect, the nitro group was connected to the electron acceptor group. The effect of the position of the nitro group and the tetrazole group linked to the benzene ring on the photophysical, electrochemical, and photovoltaic properties of sensitizers are investigated in detail. They all show intense UV–Vis absorptions around 400 nm and 510 nm. The co-sensitizations of SD-1 and SD-2 with ruthenium complex HD-2 are further evaluated and the co-sensitization results were compared with DCA. Co-sensitization of HD-2 with SD-2 was more efficient than found for co-sensitization with DCA (5.6% higher). Moreover, the influences of molecular geometry on charge recombination and photovoltaic performance of DSSCs were systematically investigated by incident photon to current efficiency (IPCE) spectra and electrochemical impedance spectroscopy (EIS) investigations.

Effect of Different Site Trifluoromethylbenzoic Acid Organic Photosensitizer for Dye‐sensitized Solar Cells

AbstractTwo novel D‐A‐π‐A triazatruxene (TAT)‐based photosensitizers with different acceptor, namely SL201 and SL202, respectively, have been successfully synthesized and applied in dye‐sensitized solar cells (DSSCs). The trifluoromethyl as strong electron‐withdrawing group was introduced to different sites of benzoic acid, in order to enhance the electron‐withdrawing ability of the acceptor, broaden the light capture ability and improve power conversion efficiency (PCE) of the DSSCs. Due to the steric hindrance effect, the molecular planarity of the trifluoromethyl group at different positions in the molecule is different, which leads to different photovoltaic performance of DSSCs. Finally, the DSSCs based on SL202 obtain a higher PCE of 9.8 %, short‐circuit current density (Jsc) of 15.3 mA/cm2, an open‐circuit voltage (Voc) of 927 mV and a fill factor (FF) of 0.69, compared with 9.0 % of SL201, using Co2+/Co3+ complex redox couple under standard AM 1.5G solar irradiation (100 mW/cm2). The same chemical group at different positions will produce different molecular planarity, further causing different photovoltaic performance of devices.

Nanocomposites of Multi-walled Carbon Nanotubes and Titanium dioxide (MWCNTs/TiO2) as affective counter electrode materials for Platinum-free Dye-Sensitized Solar Cells (DSSCs)

Platinum is commonly used as a catalyst to regenerate the redox mediator in Dye-Sensitized Solar Cells (DSSCs). This work intends to replace the expensive and rare platinum with conventional and economical materials. Nanocomposites of Multi-walled Carbon Nanotubes (MWCNTs) and TiO2 can be used as active catalyst materials for the counter-electrode of DSSC. In these composites, MWCNTs provide catalytic properties, and TiO2 acts as a binder. The interaction between MWCNTs and TiO2 has been investigated by Transmission Electron Microscopy (TEM). It has been observed that DSSCs photovoltaic performance significantly depends on the concentration of MWCNTs in nanocomposites. The amount of MWCNTs has been optimized for the best performance of DSSC. The solar cell assembled with 4%MWCNTs catalyst material showed an efficiency of 8.81%, comparable to Pt-based device (9.40%), fabricated under analogous environment.

Structural Engineering of Organic D-A-π-A Dyes Incorporated with a Dibutyl-Fluorene Moiety for High-Performance Dye-Sensitized Solar Cells.

Structural engineering of the light-harvesting dyes employed in DSSCs (dye-sensitized solar cells) with a systematic choice of the electron-donating and -accepting groups as well as the π-bridge allows the (photo)physical properties of dyes to match the criteria needed for improving the DSSC efficiency. Herein, we report an effective approach of molecular engineering of DSSC sensitizers, aiming to gain insights on the configurational impact of the fluorenyl unit on the optoelectronic properties and photovoltaic performance of DSSCs. Five new organic dyes (GZ116, GZ126, GZ129, MA1116, and MA1118) with a D-A-π-A framework integrated with a fluorenyl moiety were designed and synthesized for DSSCs. The fluorenyl unit is configured as part of the π-spacer for the GZ series, whereas it connected on the electron-deficient quinoxaline motif for the MA series. The devices fabricated from the MA1116 sensitizer produced the best performance under standard AM 1.5 G solar conditions as well as dim-light (300-6000 lx) illumination. The devices fabricated from MA1116 displayed a PCE of 8.68% (Jsc = 15.00 mA cm-2, Voc = 0.82 V, and FF = 0.71) under 1 sun and 26.81% (Jsc = 0.93 mA cm-2, Voc = 0.68 V, and FF = 0.76) under 6000 lx illumination. The device efficiency based on dye MA1116 under 1 sun outperformed that based on the standard N719 dye, whereas a comparable performance between devices based on MA1116 and N719 was achieved under dim-light conditions. A combination of enhancing the charge separation, suppressing dye aggregation, and providing better insulation that prevents the oxidized redox mediator from approaching the TiO2 surface all contribute to the superior performance of DSSCs fabricated based on these light-harvesting dyes. The judicious integration of the fluorenyl unit in a D-A-π-A-based DSSC would be a promising strategy to boost the device performance.

A novel fabrication of organic-inorganic hybridized Graphene-La2CrFeW6 nanocomposite and its improved photovoltaic performance in DSSCs

We fabricated a novel nanocomposite composed of graphene-La2CrFeW6 perovskite compounds with an organic-inorganic counter electrode based on CdSe, gallic acid, urea and sulfate in dye-sensitized solar cells (DSSCs) by a simple hydrothermal technique. The nanocomposite shows an excellent electro–catalytic activity with low charge-transfer resistance, due to the synergetic catalytic effects of the graphene sheets and La2CrFeW6 perovskite with organic-inorganic materials. The special structure of this nanocomposite also improves the active sites for reduction of triiodide ions on the counter electrodes. The photo-conversion efficiency of the DSSC fabricated using a gallic-based counter electrode reached a higher value of 10.40% under standard illumination (1 sun, 100 mW cm−2, AM 1.5), as compared to the traditional Pt electrode (7.49%). The graphene-La2CrFeW6 fabricated with an organic-inorganic based CE was also found to be more efficient than those reported in previous works, in which graphene, produced by various methods, was used as a CE material. Therefore, the present nanocomposite is considered an environmentally friendly, low-cost, and highly efficient CE material for DSSCs.

Building Double Branch Dyes with Acetylenic Bonds: An Effective Strategy to Enhance the Efficiency of Dye‐Sensitized Solar Cells

Double branch (DB) dyes could reduce intermolecular interactions and realize good photovoltaic performances. Herein, symmetric DB dyes (FSDD‐1 and FSDD‐2) featuring with one and two acetylenic bonds as the isolation groups are reported. The corresponding single branch (SB) dye FSSD‐EH is synthesized for comparison. For the adsorption spectra, bathochromic shifts and higher ε are observed for DB dyes FSDD‐1 and FSDD‐2 compared with SB dye FSSD‐EH, which suggests better light‐harvesting capabilities for the DB dyes. Dye‐sensitized solar cells (DSSCs) sensitized by DB dyes FSDD‐1 and FSDD‐2 exhibit significant increases for the Jsc and Voc compared with SB dye FSSD‐EH, so much better η are achieved by the DB dyes (5.34, 7.14, and 2.46% for FSDD‐1, FSDD‐2, and FSSD‐EH, respectively). FSDD‐2 with a diyne unit exhibits higher η compared with FSDD‐1 with an yne unit as the isolation groups. The research shows that a much better photovoltaic performance of DSSCs can be achieved after connecting two dye molecules to be a DB dye by adopting acetylenic bonds as the isolation group. A longer distance between the two branches realized by a diyne unit is beneficial and effective to achieve better photovoltaic performance.

Performance evaluation of natural native dyes as photosensitizer in dye-sensitized solar cells

In this paper, the efficacy of wild natural dyes as the sensitizer was investigated for the fabrication of natural dye-sensitized solar cells (DSSCs). The natural pigments were extracted from Crocus sativus (Saffron), Allium cepa L (red onion), Malva sylvestris (Mallow), and Oregano (Origanum vulgare) using solvent extraction method. Based on the UV–vis results, the extracted solutions have been shown to contain anthocyanin or chlorophylls pigments, which are excellent pigments required for the charge-carriers generation in the energy harvesting process from the sunlight. The efficacy of all sensitizers has been evaluated using the cyclic voltammetry and current-voltage open circuit experiments of the fabricated DSSCs. The photovoltaic performance of DSSCs in terms of efficiency, current, voltage, and filling factors was performed under standard illumination of AM 1.5G having an irradiance of 100 m W c m − 2 . The results showed that the photoelectric conversion efficiency of the fabricated DSSCs were nearly less than 2%, while the open-circuit voltage and short-circuit current density were from 0.43 to 0.55 V and 0.45–0.54 mAcm -2 , respectively. The appropriate LUMO energy level and the band-gap of these extracted dyes would enable them to become efficient sensitizer for utilizing in fabricated DSSCs. Therefore, due to the existence of carbonyl and hydroxyl groups in dye's chemical structures, it enable them to bind to the T i O 2 layer, consequently, improve the electron transfer, and enhance the energy conversion efficiency of the fabricated DSSC. ● Dye extracted from natural native plants used as sensitizer for TiO2 based dye-sensitized solar cells (DSSCs). ● The efficiency of fabricated natural-DSSC is comparable with the reference cell. ● The potential of dye extraction from four native plants Crocus sativus (Saffron(, Allium cepa L (red onion), Malva sylvestris (Mallow), and Oregano (Origanum vulgare) was evaluated by effectiveness on the fabricated DSSCs.

Synthesis of Zn(II) porphyrin dyes and revealing an influence of their alkyl substituents on performance of dye-sensitized solar cells

In this study, the series of A3B-type zinc porphyrin dyes have been synthesized for dye-sensitized solar cells (DSSC). All the received zinc-porphyrin complexes bear different alkyl substituents (none, tert-butyl-, methoxy-, hexyloxy-, dodecyloxy-, a pair of hexyloxy-), bulky electron-donating substituent (diphenylamino) in each of three meso-phenyl rings and carboxylic acid as acceptor/anchoring group. The influence of the number and length of alkyl chains on the photophysical properties and DSSCs photovoltaic performance was investigated, as well as quantum-chemical modeling was carried out. Our results reveal that the alkyl chains length and number affect cell performance. We found that DSSC power conversion efficiency increases with an increase in the length and number of alkyl substituents in the porphyrins. A maximum efficiency of 1.29 % was observed in solar cells with dodecyloxy-substituted zinc porphyrin.

Graphene/polyaniline nanocomposite as platinum-free counter electrode material for dye-sensitized solar cell: its fabrication and photovoltaic performance

In this study, it was aimed to produce graphene/polyaniline nanocomposite thin films as counter electrode materials by PECVD system and to determine the photovoltaic performances of these counter electrodes in dye-sensitized solar cells (DSSCs). Graphene/polyaniline counter electrode (GPCE) material was produced in two different steps. Firstly, a single-layer and multilayer graphene thin films were produced on the fluorine-doped tinoxide (FTO) substrates. Then, polyaniline (PANI) thin films were grown on each graphene thin films using plasma polymerization technique, and eventually the production of the graphene/PANI nanocomposite was completed. The fabricated graphene/PANI nanocomposites were used in place of platinum (Pt)-counter electrode which is widely used in DSSCs and the photovoltaic performance of these counter electrodes was investigated. The DSSCs consisted of titanium dioxide (TiO2) nanotube photoanode, N719 dye, iodolyte liquid electrolyte, and graphene/PANI nanocomposite counter electrode. I–V measurements were carried out in order to calculated photoconversion efficiency (PCE) and it was found that the these efficiency of GPCEs changed between 0.56 and 1.36% according to the number of graphene layers. The photovoltaic performance of DSSC, consisting of TiO2 nanotube photoanode and Pt-counter electrode was 1.1%.

Effect of Ligand Structures of Copper Redox Shuttles on Photovoltaic Performance of Dye-Sensitized Solar Cells.

In recent years, copper(I/II) complexes have emerged as alternative redox shuttles in dye-sensitized solar cells (DSSCs), exhibiting more positive redox potential than iodine- and cobalt-based redox shuttles. In particular, copper(I/II) complexes with 1,10-phenanthroline- or 2,2'-bipyridyl-based ligands attained moderate to high power conversion efficiencies (6-11%) with a high open-circuit voltage (VOC) over 1.0 V due to the positive potentials. Although copper(I/II) complexes with 1,10-phenanthroline-based ligands with 2,9-substituents have been developed, the effect of their ligand structures on the photovoltaic performance of DSSCs have not been fully addressed due to limited synthetic access to 1,10-phenanthroline derivatives. In this study, we designed and synthesized a series of copper(I/II) complexes with 1,10-phenanthroline ligands with different substituents at the 2,9-positions: bis(2-n-butyl-1,10-phenanthroline)copper(I/II) ([Cu(bp)2]1+/2+), bis(2-ethyl-9-methyl-1,10-phenanthroline)copper(I/II) ([Cu(emp)2]1+/2+), bis(2,9-diethyl-1,10-phenanthroline)copper(I/II) ([Cu(dep)2]1+/2+), and bis(2,9-diphenyl-1,10-phenanthroline)copper(I/II) ([Cu(dpp)2]1+/2+). The more positive redox potentials of [Cu(emp)2]1+/2+ and [Cu(dep)2]1+/2+, compared to that of bis(2,9-dimethyl-1,10-phenanthroline)copper(I/II) ([Cu(dmp)2]1+/2+), originate from the larger steric hindrance of the ethyl group instead of the methyl group, whereas the redox potential of [Cu(bp)2]1+/2+ is significantly shifted to the negative direction because of the lower steric hindrance of the 2-monosubstituted 1,10-phenanthroline ligands. The efficiency of the DSSC with [Cu(bp)2]1+/2+ (5.90%) is almost comparable to the DSSC with [Cu(dmp)2]1+/2+ (6.29%). In contrast, the DSSCs with [Cu(emp)2]1+/2+ (3.25%), [Cu(dep)2]1+/2+ (2.56%), and [Cu(dpp)2]1+/2+ (2.21%) exhibited lower efficiencies than those with [Cu(dmp)2]1+/2+ and [Cu(bp)2]1+/2+. The difference can be rationalized by the electron collection efficiencies. Considering the similar photovoltaic properties of the DSSCs with [Cu(bp)2]1+/2+ and [Cu(dmp)2]1+/2+, the use of copper(I/II) complexes with 2-monosubstituted 1,10-phenanthroline ligands as the redox shuttle may be useful to improve the short-circuit current density while retaining the rather high VOC value when dyes with a smaller bandgap (i.e., better light harvesting) are developed.

Molecular Engineering of Quinodimethane-based Dyes with Different Anchor Groups for Dye Sensitized Solar Cells (DSSCs)

This paper mainly works on changing different anchoring groups of quinodimethane-based dyes, which represent a twisting phenyl ring during the excitation process, for dye-sensitized solar cells (DSSCs). Five different groups, (1) cyanoacrylic acid (-CHC(CN)COOH), (2) carboxylic acid (-COOH), (3) pyridine (-C5H5N), (4) sulfonic acid (-SO3H), (5) phosphoric acid (-PO3H2), were adopted as anchors on the quinodimethane moieties forming dyes 1-5, to further explore their effects on optoelectronic properties via molecular engineering methods. Density functional theory (DFT) and time-dependent DFT (TD-DFT) were used to calculate their electronic structures and electro-optical properties. Computational results show that all dyes show suitable molecular orbital energy levels between the conductive band of TiO2 and the potentials I-/I3- redox couple so that all of 1-5 can be potential candidates for DSSCs application. Also, TDDFT results exhibit that dye 1 has the widest absorption band in UV-visible region, with the first excitation energies of 2.782 eV, while other dyes show similar first excitation energies about 0.2 eV higher than that of dye 1. In particular, dye 3 with pyridine as anchor group shows a very excellent charge transfer properties from the highest occupied molecular orbitals (HOMO) to the lowest unoccupied molecular orbitals (LUMO), with the highest HOMO level of -5.16 eV, which offers a strong driving force for dye regeneration, and a LUMO level of -2.36 eV, which enables excited electrons successfully to be injected in to titania film. Also, this pyridine anchor group offers a larger π conjugation, which may improve the ability of electron injecting and further strengthen the photovoltaic performance in DSSCs.

Development of Y2O3: Ho3+/Yb3+ Upconverting Nanophosphors for Enhancing Solar Cell Efficiency of Dye-Sensitized Solar Cells

Light scattering behavior of dye-sensitized solar cells (DSSCs) containing Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> : Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> /Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> upconverting (UC) nanophosphor has been studied. To study the influence of UC nanophosphors on photovoltaic performance of DSSCs, UC nanophosphors have been introduced into the TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film to form the hybrid film. The electron ejection ability, current density (JSC ), open-circuit voltage (VOC ), and power conversion efficiency (PCE) of DSSCs have been determined. The enhancement of about 31% and 30% for JSC and PCE in DSSCs hybrid film compared with that of DSSCs TiO2 film has been observed due to improved near infrared to visible light harvesting properties of UC nanophosphors.