Novel conjugated organic dyes containing bis-dimethylfluorenyl amino phenyl thiophene for efficient solar cell

Two novel organic dyes (JK-5 and JK-6) containing bis-dimethylfluorenyl amino phenyl thiophene and additional methine unit are synthesized. Nanocrystalline TiO₂ dye-sensitized solar cell was fabricated using these dyes. A solar-to-electric conversion efficiency of 5.12% and 4.78% is achieved with JK-5 and JK-6, respectively.     

Novel organic dyes containing bis-dimethylfluorenyl amino benzo[b]thiophene for highly efficient dye-sensitized solar cell

Novel organic dyes, JK-16 and JK-17 containing bis-dimethylfluorenyl amino benzo[b]thiophene are designed and synthesized. Under standard global AM 1.5 solar condition, the JK-16 sensitized cell gave a short circuit photocurrent density (J_sc) of 15.33 mA cm⁻², open circuit voltage (V_oc) of 0.74 V, and a fill factor of 0.66, corresponding to an overall conversion efficiency η of 7.43%, and the JK-17 sensitized cell gave a J_sc of 12.66 mA cm⁻², V_oc of 0.67 V, and a fill factor of 0.65, corresponding to an overall conversion efficiency η of 5.49%.     

Molecular engineering of organic dyes containing N-aryl carbazole moiety for solar cell

Organic dyes containing N-aryl carbazole moiety are designed and synthesized. Under standard global AM 1.5 solar condition, the JK-25 sensitized cell gave a short circuit photocurrent density (J_sc) of 11.50 mA cm⁻², an open circuit voltage (V_oc) of 0.68 V, a fill factor of 0.66, corresponding to an overall conversion efficiency η of 5.15%, and the maximum incident monochromatic photon-to-current conversion efficiency (IPCE) of 77% at 430 nm.     

Extraction of water miscible organic dyes by reverse micelles of alkyl glucosides

The extraction of methyl orange or methylene blue from an aqueous phase to an organic phase of reverse micelles of alkyl glucosides was investigated. Dodecyl glucoside, a biodegradable and biocompatible surfactant, was employed as a kind of alkyl glucosides, since a stable Winsor II system consisting of the water-in-oil type microemulsion and aqueous phases was formed when an organic solution containing dodecyl glucoside was contacted with an aqueous solution. The water content in the reverse micellar organic phase increased with an increase in the concentration of dodecyl glucoside. The extraction ratio of dyes also increased with increasing the concentration of dodecyl glucoside. Furthermore, the extraction ratio of dyes was dramatically dependent upon the pH of an aqueous phase and temperature.     

Molecular engineering of organic sensitizers containing indole moiety for dye-sensitized solar cells

Three organic dyes, JK-77, JK-78, and JK-79 containing indole unit are designed and synthesized. Nanocrystalline TiO₂ dye-sensitized solar cells were fabricated using these dyes. Under standard global AM 1.5 solar condition, the JK-79 sensitized solar cell gave a short circuit photocurrent density of 13.62 mA cm⁻², open-circuit voltage of 0.705 V, and a fill factor of 0.74, corresponding to an overall conversion efficiency η of 7.18%. We found that the η of JK-79 was higher than those of other two cells due to the higher V_oc. The improved V_oc value is attributed to the suppression of dark current owing to the blocking effect of a long alkyl chain.     

Synthesis of new julolidine dyes having bithiophene derivatives for solar cell

Three novel organic dyes containing julolidine and bithiophene derivatives were synthesized. Nanocrystalline TiO₂ dye-sensitized solar cells were fabricated using these dyes. A solar-to-electric conversion efficiency of 2.95% is achieved with JK-14. We found that the power conversion efficiency was shown to be quite sensitive to the structural variations of bridging bithiophene moiety.     

Synthesis and photovoltaic properties of novel organic sensitizers containing indolo[1,2-f]phenanthridine for solar cell

Organic dyes containing indolo[1,2-f]phenanthridine unit are a promising new class of sensitizers for dye-sensitized solar cells, as a result of their broad and intense visible absorptions. Under standard global AM 1.5 solar condition, the JK-61 sensitized cell gave a short circuit photocurrent density (J_sc) of 15.81 mA cm⁻², an open circuit voltage (V_oc) of 0.73 V, a fill factor of 0.72, corresponding to an overall conversion efficiency of 8.34%.     

Fluorine substituent effect on organic dyes for sensitized solar cells

Two sets of organic dyes containing a stilbene backbone with fluorine substituents were designed for a study on the quantum efficiency of dye-sensitized solar cells (DSSCs). The results revealed that adding a fluorine substituent on the phenyl group ortho to the cyanoacrylate can enhance the light-harvesting performance in comparison with the unsubstituted one. However, when the two ortho-positions were both substituted by fluorine atoms, the performance of DSSCs was substantially reduced. The reason was mainly ascribed to a distortion from a planar geometry caused by steric hindrance. The π-conjugation was therefore disturbed, and the result led to a substantial reduction of the short-circuit photocurrent density (J_sc). Another effect was found that the open-circuit photovoltage (V_oc) of the doubly substituted derivative was lower than that of the mono-substituted one. The more flexible conformation of the difluoro-substituted dyes induced an undesired nonradiative decay, therefore led to a reduction of open-circuit photovoltage. The phenomenon can be verified by electrochemical impendence spectrum. The non-planar geometry was realized by a computation using the density function theory (DFT) model. The slight blue shift of absorption band was also consistent with the calculated transition energy by a time dependent DFT model.     

Modifying transparent electrode with conjugated organic semiconductor hole transport material as interface for enhancing performance of organic solar cell

Indium tin oxide (ITO) is used as a substrate was covered with 4-[4-(4-methoxy-N-naphthalen-2-ylanilino) phenyl] benzoic acid (MNA) as a self-assembled monolayer (SAM). Poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6) C₆₁ (PCBM) were mixed and used as a donor–acceptor in organic solar cell (OSC). The MNA (SAM) layer is used as an interface instead of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) for hole injection. The HOMO-LUMO energy level of MNA-SAM molecule and the electronic charge distribution were calculated theoretically using Chemissian software. The HOMO-LUMO energy level of the MNA is calculated as E_HOMO = ?5.10 eV and E_LUMO = ?1.60 eV. The OSC modified with MNA showed an efficient performance in the absence of PEDOT: PSS as hole transport layer. The annealing of the ITO/SAM/P3HT: PCBM films at different temperatures are also investigated to study the effect of reducing defects. The interface structures of the organic semiconductor layer on ITO were characterized by Atomic Force Microcopy (AFM). In addition, Kelvin Probe Microscopy (KPM) is used to understand how the annealing changes the surface potential energy of the ITO/SAM substrate. Using the KPM method, which measures the surface potential energy of the films, the energy bands of the ITO were increased to maximum 5.09 eV. The ITO/SAM/P3HT: PCBM film's surface potential was determined to be 0.18 eV after being annealed at 80 °C. The surface potential of the modified films was discovered to be 0.33 V and 0.39 V when the annealing temperature was raised from 80 °C to 120 °C and 160 °C. The maximum device efficiency was demonstrated by the ITO/SAM/P3HT: PCBM film after an hour of annealing at 160 °C.     

Unsymmetrical zinc phthalocyanines containing thiophene and amine groups as donor for bulk heterojunction solar cells

Photovoltaic technology is an alternative resource for renewable and sustainable energy and low costs organic photovoltaic devices such as bulk-heterojunction (BHJ) solar cells, which are selective candidates for the effective conversion of solar energy into electricity. Asymmetric phthalocyanines containing electron acceptor and donor groups create high photovoltaic conversion efficiency in dye sensitized solar cells. In this study, a new unsymmetrical zinc phthalocyanine was designed and synthesized including thiophene and amine groups at peripherally positions for BHJ solar cell. The structure of the targeted compound (4) was characterized comprehensively by FT-IR, UV–Vis, ¹H-NMR, and MALDI-TOF MS spectroscopies. The potential of this compound in bulk heterojunction (BHJ) photovoltaic devices as donor was also researched as function of blend ratio (blend ratio was varied from 0.5 to 4). For this purpose, a series of BHJ devices with the structure of fluorine doped indium tin oxide (FTO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/ ZnPc:[6,6]- phenyl-C61- butyric acid methyl ester (PCBM) blend/Al with identical thickness of ZnPc:PCBM layer were fabricated and characterized. Photo current measurements in 4 revealed that the observed photo current maximum is consistent with UV-vis spectra of the compound of 4. Preliminary studies showed that the blend ratio has a critical effect on the BHJ device performance parameters. Photovoltaic conversion efficiency of 6.14% was achieved with 4 based BHJ device.     

Furan-containing conjugated polymers for organic solar cells

Development of organic semiconductors is one of the most intriguing and productive topics in material science and engineering. Many efforts have been made on the synthesis of aromatic building blocks such as benzene, thiophene and pyrrole due to the facile preparation accompanied by the intrinsic environmental stability and relatively efficient properties of the resulting polymers. In the past, furan has been less explored in this field because of its high oxidation potential. Recently, furan has attracted obsession due to its weaker aromaticity, the greater solubilities of furan-containing π-conjugated polymers relative to other benzenoid systems and the accessibility of furan-based starting materials from renewable resources. This review elaborates the advancements of organic photovoltaic polymers containing furan building blocks. The uniqueness and advantages of furan-containing building blocks in semiconducting materials are also discussed.     

Functionalized organic dyes containing a phenanthroimidazole donor for dye-sensitized solar cell applications

Five functionalized organic dyes (H6-10) containing a phenanthroimidazole unit as an electron donor were synthesized and characterized for use in dye-sensitized solar cell (DSSC) applications. Under standard global AM 1.5 solar conditions, the DSSCs based on dye H6 displayed the best performance, with an incident photon-to-current conversion efficiency (IPCE) exceeding 70% at wavelengths of 400–530 nm, a short-circuit photocurrent density of 10.98 mA cm^?2, an open-circuit voltage of 0.68 V, a fill factor of 0.69, and an overall conversion efficiency of 5.12%. This efficiency is ～94% of that for JK2 cells (5.46%) and ～72% of that for N719 cells (7.07%) under the same conditions.     

Synthesis and the effect of alkyl chain length on photochromic properties of diarylethene derivatives

A new class of photochromic diarylethenes bearing pyrrole and thiophene units with different length of alkyl chains at 2-position of thiophene rings have been synthesized. Their characteristics, including photochromism and fatigue resistance were investigated systematically, and each diarylethene derivative showed good photochromic properties whether in solution or in PMMA films. The alkyl group moiety was connected directly to the central cyclopentene ring as a heteroaryl unit and availably participated in photoisomerization reaction. And some properties, for example, the conversion ratio in the photostationary state(PSS) and the absorption coefficient of the ring-closed isomers in acetonitrile were significantly affected by the alkyl chain length. The results revealed that substituents of alkyl chain played an important role in the photoisomerization process of diarylethenes.     

Tetrazole thiolate/disulfide organic redox couples carrying long alkyl groups in dye-sensitized solar cells with Pt-free electrodes

Colorless tetrazole thiolate/sulfide redox couples carrying long alkyl groups, such as n-butyl, n-hexyl, and n-octyl groups, were synthesized as electrolytes in iodine/iodide-free dye-sensitized solar cells (DSSCs). Among N719/TiO₂-based DSSCs employing these highly soluble redox couples for 3-methoxypropionitrile (3-MPN) and ionic liquid with PEDOT counter electrode, the DSSC with n-hexyl redox analogue gave an optimized η value of 4.32%. An observed respectable quantum efficiency for 400–500 nm light is in sharp contrast to the decreased performance for iodine/iodide systems that originates from the substantial light absorption of iodine. On the other hand, the redox possessing n-octyl group significantly lowered the cell performance, which could be a result of the much increased resistance of electrolyte diffusion in the DSSC.     

An iterative approach toward the synthesis of discrete oligomeric p-phenylene vinylene organic dyes employing aqueous Wittig chemistry

Photovoltaic research has become increasingly prominent as the search for alternatives to fossil fuels are actively sought. A novel process for the iterative synthesis of discrete donor/acceptor-flanked oligostilbenes, key constituents in dye-sensitized solar cells, is described. The aqueous Wittig process is high yielding, proceeds with high (E)-stereoselectivity and allows facile product purification.     

Synthesis and photovoltaic properties of organic sensitizers containing electron-deficient and electron-rich fused thiophene for dye-sensitized solar cells

Diverse fused thiophenes with electron-rich and electron-deficient blocks have been synthesized and employed as the π-conjugated spacers of organic dyes for the dye-sensitized solar cells (DSSCs). The effects of these fused thiophenes were investigated by their absorption spectra, electrochemical and photovoltaic properties. For a typical device a maximum power conversion efficiency of 6.11% was obtained under simulated AM 1.5 irradiation (100 mW cm^?2): a short-circuit current (J_SC) of 14.47 mA cm^?2, an open-circuit voltage (V_OC) of 670 mV, and a fill factor (FF) of 0.63.     

Molecular design of organic dyes based on vinylene hexylthiophene bridge for dye-sensitized solar cells

Three donor-(π-spacer)-acceptor (D-π-A) organic dyes, containing different groups (triphenylamine, di(p-tolyl)phenylamine, and 9-octylcarbazole moieties) as electron donors, were designed and synthesized. Nanocrystalline TiO₂ dye-sensitized solar cells were fabricated by using these dyes. It was found that the variation of electron donors in the D-π-A dyes played an important role in modifying and tuning photophysical properties of organic dyes. Under standard global AM 1.5 solar condition, the DSSC based on the dye D2 showed the best photovoltaic performance: a short-circuit photocurrent density (J _sc ) of 13.93 mA/cm², an open-circuit photovoltage (V _oc ) of 0.71 V, and a fill factor (FF) of 0.679, corresponding to solar-to-electric power conversion efficiency (η) of 6.72%. Supported by the Key Project of Hunan Province of China (Grant No. 2008FJ2004), Natural Science Foundation of Hunan Province of China (Grant Nos. 09JJ3020 & 09JJ4005), and Scientific Research Fund of Hunan Provincial Education Department (Grant No. 08C888).     

Synthesis and characterization of organic dyes containing 4,5-diazafluorene as efficient sensitizers for dye-sensitized solar cells

Two dyes which are 4,5-diazafluoren-9-one-derived diimine ligands and their corresponding Ru(II) bipyridine complexes were synthesized. The structures of all compounds were determined by FTIR, UV–Vis, ¹H-NMR, ¹C-NMR, and MS spectroscopic data. The photovoltaic and electrochemical properties of these compounds were investigated and the applicability in DSSCs as photosensitizers was studied. The photovoltaic cell efficiencies (PCE) of the devices were 0.36–1.26% under simulated AM 1.5 solar irradiation of 100 mW/cm², and the highest open-circuit voltage (V_oc) reached 0.34 V. When comparing the photovoltaic performance of DSSC devices, efficiency increases L2 < L2-Ru < L1 < L1-Ru. The PCE value of 1.26% was obtained with a DSSC based on L1-Ru under AM irradiation (100 mW/cm²). DSSC based on L1-Ru produced efficiency of 1.26%, whereas DSSC-based L1 exhibited the device performance with efficiency of 0.84% under illumination. These results show that the availability of a π-conjugated bridge and a richer electron donor for photovoltaic performance of the DSSC provides increased efficiency.     

Highly efficient substituted triple rhodanine indoline dyes in zinc oxide dye-sensitized solar cell

Substituited triple rhodanine indoline dyes showed higher performance than known triple rhodanine derivative (D150). A few triple rhodanine indoline derivatives showed comparable conversion efficiency to D149.     

Synthesis of new truxene based organic sensitizers for iodine-free dye-sensitized solar cells

Developing arylamine photosensitizers with high extinction coefficients, proper electronic structures, and steric properties is warranted for the dye-sensitized solar cells (DSCs) employing iodine-free redox shuttles. Two new organic sensitizers (M21 and M22) featuring unsymmetrical truxene-based triarylamine donor have been synthesized and compared to its reference sensitizer M4. The effects of unsymmetrical truxene-based triarylamine donors were investigated by their absorption spectra, electrochemical and photovoltaic properties. The incorporation of strong electron donor unit (i.e., dipropylfluorene and 4-methoxybiphenyl) has resulted in an improved light harvesting capacity, and thus photocurrent as well as efficiency of cells. M22 sensitized DSCs employing the Co(II/III)tris(1,10-phenanthroline)-based redox electrolyte affords a short circuit photocurrent of 13.1 mA cm⁻², an open circuit voltage of 861 mV, and a fill factor of 0.70, corresponding to an overall conversion efficiency of 7.89% under standard AM 1.5 sunlight.