Synthesis and photovoltaic properties of polymeric metal complexes containing 8-hydroxyquinoline as dye sensitizers for dye-sensitized solar cells

Four new donor–acceptor type polymeric metal complexes (P1, P2, P3, and P4) with the same Cd(II) complex in side chain and different conjugated backbone structures were synthesized by Yamamoto coupling and applied in dye-sensitized solar cells (DSSCs) as photosensitizers. The photophysical, electrochemical, and thermal properties were investigated in detail, showing that conjugated backbone containing fluorene improved intramolecular charge transfer and increased generation of photocurrent. The highest power conversion efficiency of 0.56% (J _sc?=?1.63?mA?cm^?2, V _oc?=?0.69?V, FF?=?0.50) was obtained with a DSSC based on P3 under simulated air mass 1.5 G solar irradiation, which shows a new strategy to design photosensitizers for DSSCs.     

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 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.     

Anionic benzothiadiazole containing polyfluorene and oligofluorene as organic sensitizers for dye-sensitized solar cells

Anionic polyfluorene and oligofluorene derivatives were synthesized and utilized as organic dye sensitizers in dye sensitized solar cells to show a maximum power conversion efficiency of 1.39%.     

Novel quinoxaline-based organic sensitizers for dye-sensitized solar cells

Novel quinoxaline-based organic sensitizers using vertical (RC-21) and horizontal (RC-22) conjugation between an electron-donating triphenylamine unit and electron-accepting quinoxaline unit have been synthesized and used for dye-sensitized solar cells (DSSCs), leading to the relatively high power conversion efficiencies of 3.30 and 5.56% for RC-21 and RC-22, respectively. This result indicates that the quinoxaline electron-accepting unit is quite a promising candidate in organic sensitizers.     

Molecular engineering of organic sensitizers containing p-phenylene vinylene unit for dye-sensitized solar cells

Three organic sensitizers containing bis-dimethylfluorenyl amino donor and a cyanoacrylic acid acceptor bridged by p-phenylene vinylene unit were synthesized. The power conversion efficiency was quite sensitive to the length of bridged phenylene vinylene groups. A nanocrystalline TiO2 dye-sensitized solar cell was fabricated using three sensitizers. The maximum power conversion efficiency of JK-59 reached 7.02%.     

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.     

Perylene anhydride fused porphyrins as near-infrared sensitizers for dye-sensitized solar cells

Two perylene anhydride fused porphyrins 1 and 2 have been synthesized and employed successfully in dye-sensitized solar cells (DSCs). Both compounds showed broad incident monochromatic photon-to-current conversion efficiency spectra covering the entire visible spectral region and even extending into the near-infrared (NIR) region up to 1000 nm, which is impressive for ruthenium-free dyes in DSCs.     

Synthesis of sensitizers containing donor cascade of triarylamine and dimethylarylamine moieties for dye-sensitized solar cells

Four triarylamine derivatives (XS6-9) containing N,N-dimethylaryl amine units as secondary electron-donating groups are designed and synthesized. These dyes were applied into nanocrystalline TiO₂ dye-sensitized solar cells through standard operations. For a typical device the maximal monochromatic incident photon-to-current conversion efficiency (IPCE) can reach 93%, with a short-circuit photocurrent density (J_sc) 10.8 mA cm⁻², an open-circuit photovoltage (V_oc) 690 mV, and fill factor (FF) 0.61, which corresponds to an overall conversion efficiency of 4.54%.     

Synthesis and photovoltaic properties of new [1,2,5]thiadiazolo[3,4-c]pyridine-based organic Broadly absorbing sensitizers for dye-sensitized solar cells

In this paper, by introducing [1,2,5]thiadiazolo[3,4-c]pyridine (PT) as an auxiliary acceptor into the molecular design of organic sensitizers, we have synthesized four new dyes (PT1–PT4) for dye-sensitized solar cells (DSSCs) with triphenylamine or N,N-diphenylthiophen-2-amine as the donor units and thiophene or benzene as the π-bridges, respectively. All the structures, optical and electrochemical properties were fully characterized. Nanocrystalline TiO₂ dye-sensitized solar cells were also fabricated using these dyes. Among them, PT2-based DSSCs showed the highest overall conversion efficiency of 6.11% with V_oc=668 mV, J_sc=12.61 mA cm⁻² and a fill factor (FF)=0.74 after a chenodeoxycholic acid (CDCA) treatment under standard illumination condition (100 mW cm⁻² simulated AM 1.5 solar light).     

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%.     

Molecular engineering of organic sensitizers for dye-sensitized solar cell applications

Novel unsymmetrical organic sensitizers comprising donor, electron-conducting, and anchoring groups were engineered at a molecular level and synthesized for sensitization of mesoscopic titanium dioxide injection solar cells. The unsymmetrical organic sensitizers 3-(5-(4-(diphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D5), 3-(5-bis(4-(diphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D7), 5-(4-(bis(4-methoxyphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D9), and 3-(5-bis(4,4'-dimethoxydiphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D11) anchored onto TiO2 and were tested in dye-sensitized solar cell with a volatile electrolyte. The monochromatic incident photon-to-current conversion efficiency of these sensitizers is above 80%, and D11-sensitized solar cells yield a short-circuit photocurrent density of 13.90 +/- 0.2 mA/cm(2), an open-circuit voltage of 740 +/- 10 mV, and a fill factor of 0.70 +/- 0.02, corresponding to an overall conversion efficiency of 7.20% under standard AM 1.5 sun light. Detailed investigations of these sensitizers reveal that the long electron lifetime is responsible for differences in observed open-circuit potential of the cell. As an alternative to liquid electrolyte cells, a solid-state organic hole transporter is used in combination with the D9 sensitizer, which exhibited an efficiency of 3.25%. Density functional theory/time-dependent density functional theory calculations have been employed to gain insight into the electronic structure and excited states of the investigated species.     

Novel organic dye sensitizers containing fluorenyl and biphenyl moieties for solar cells

Three novel triarylamine dyes(AFL1-AFL3) containing fluorenyl and the biphenyl moieties have been designed and synthesized for application in dye-sensitized solar cells.The light-harvesting capabilities and photovoltaic performance of these dyes were investigated systematically through comparison of different π-bridges.The dye with a furan linker exhibited a higher open-circuit voltage(V_(OC)) and monochromatic incident photon-to-current conversion efficiency(IPCE) compared to thiophene and benzene linker.Thus,AFL3 containing a furan linker exhibited the maximum overall conversion efficiency of 5.81%(V_(OC) = 760 mV,J_(SC) = 11.36 mA cm~2 and ff=0.68) under standard global AM 1.5 G solar condition.     

New bithiazole-based sensitizers for efficient and stable dye-sensitized solar cells

A series of new push-pull organic dyes (BT-I-VI), incorporating electron-withdrawing bithiazole with a thiophene, furan, benzene, or cyano moiety, as π?spacer have been synthesized, characterized, and used as the sensitizers for dye-sensitized solar cells (DSSCs). In comparison with the model compound T1, these dyes containing a thiophene moiety between triphenylamine and bithiazole display enhanced spectral responses in the red portion of the solar spectrum. Electrochemical measurement data indicate that the HOMO and LUMO energy levels can be tuned by introducing different π?spacers between the bithiazole moiety and cyanoacrylic acid acceptor. The incorporation of bithiazole substituted with two hexyl groups is highly beneficial to prevent close π-π aggregation, thus favorably suppressing charge recombination and intermolecular interaction. The overall conversion efficiencies of DSSCs based on bithiazole dyes are in the range of 3.58 to 7.51?%, in which BT-I-based DSSCs showed the best photovoltaic performance: a maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 81.1?%, a short-circuit photocurrent density (J(sc)) of 15.69?mA?cm(-2), an open-circuit photovoltage (V(oc)) of 778?mV, and a fill factor (ff) of 0.61, which correspond to an overall conversion efficiency of 7.51?% under standard global AM 1.5 solar light conditions. Most importantly, long-term stability of the BT-I-III-based DSSCs with ionic-liquid electrolytes under 1000?h of light soaking was demonstrated and BT-II with a furan moiety exhibited better photovoltaic performance of up to 5.75?% power conversion efficiency.     

Phthalocyanines: colorful macroheterocyclic sensitizers for dye-sensitized solar cells

Abstract  

Dye-sensitized solar cells (DSSCs) have gained great attention as lower-cost alternatives to conventional photovoltaic devices. One way to improve the excellent efficiencies (ca. 11%) exhibited by DSSCs based on ruthenium polypyridyl dyes would consist in using sensitizers with enhanced light-harvesting properties in the red region of the spectrum. Phthalocyanines (Pcs) are very robust molecules which present extraordinary high extinction coefficients in the 600- to 700-nm spectral region. Intensive research has been focused on reducing the undesired aggregation phenomena of Pcs on the metal oxide surface, while keeping a good electronic coupling between the LUMO of the Pcs and the TiO₂ conduction band, and a good solubility of the dye in organic solvents. Recently, unsymmetrically substituted “push–pull” Pcs have emerged as efficient red-absorbing dyes, reaching power conversion efficiencies of up to 4.7%, when used as single sensitizers.     

Low-bandgap donor-acceptor conjugated polymer sensitizers for dye-sensitized solar cells

A set of two donor-acceptor type conjugated polymers with carboxylic acid side groups have been synthesized and utilized as active materials for dye-sensitized solar cells (DSSCs). The polymers feature a π-conjugated backbone consisting of an electron-poor 2,1,3-benzothiadiazole (BTD, acceptor) unit, alternating with either a thiophene-fluorene-thiophene triad (2a) or a terthiophene (3a) segment as the donor. The donor-acceptor polymers absorb broadly throughout the visible region, with terthiophene-BTD polymer 3a exhibiting an absorption onset at approximately 625 nm corresponding to a ～1.9 eV bandgap. The polymers adsorb onto the surface of nanostructured TiO(2) due to interaction of the polar carboxylic acid units with the metal oxide surface. The resulting films absorb visible light strongly, and their spectra approximately mirror the polymers' solution absorption. Interestingly, a series of samples of 3a with different molecular weight (M(n)) adsorb to TiO(2) to an extent that varies inversely with M(n). DSSCs that utilize the donor-acceptor polymers as sensitizers were tested using an I(-)/I(3)(-) electrolyte. Importantly, for the set of polymer sensitizers 3a with varying M(n), the DSSC efficiency varies inversely with M(n), a result that reflects the difference in adsorption efficiency observed in the film absorption experiments. The best DSSC cell tested is based on a sample of 3a with M(n) ～ 4000, and it exhibits a ～65% peak IPCE with J(sc) ～12.6 mA cm(-2) under AM1.5 illumination and an overall power conversion efficiency of ～3%.     

Synthesis and photovoltaic properties of efficient organic dyes containing the benzo[b]furan moiety for solar cells

New organic dyes composed of the benzo[b]furan donor, thiophene-conjugated bridge, and cyano acrylic acid acceptor have been newly synthesized through the one-pot coupling cyclization key step. Nanocrystalline TiO2 dye-sensitized solar cell was fabricated using this dye. A solar-to-electric conversion efficiency of 6.65% and 4.70% is achieved with 1 and 2, respectively.     

Synthesis of conjugated organic dyes containing alkyl substituted thiophene for solar cell

Three organic dyes, JK-41, JK-42, and JK-43 containing bis-dimethylfluoreneaniline and alkyl substituted thiophene unit are designed and synthesized. Under standard global AM 1.5 solar condition, the JK-41 sensitized cell gave a short circuit photocurrent density (J_sc) of 15.23 mA cm⁻², open circuit voltage (V_oc) of 0.67 V, and a fill factor of 0.67, corresponding to an overall conversion efficiency η of 7.69%. Molecular-orbital calculations of the three dyes suggest that the electron distribution moves from the aniline derivative to the cyanoacrylic acid moiety. We found that the power conversion efficiency was shown to be quite sensitive to the structural variations of alkyl substituted thiophene moiety.