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.     

Highly efficient new indoline dye having strong electron-withdrawing group for zinc oxide dye-sensitized solar cell

New indoline dye (DN319) having strong electron-withdrawing dicyanovinylidene moiety and octyl group in the terminal rhodanine ring gave higher efficiency than D205, which was known as an excellent organic dye sensitizer. This result is attributed to the bathochromic shift in the UV-vis absorption band and positive shift in the E_ox level of DN319.     

High efficiency of dye-sensitized solar cells based on metal-free indoline dyes

We now report metal-free organic dyes having a new type of indoline structure, which exhibits high efficiencies in dye-sensitized solar cells. The solar energy to current conversion efficiencies with the new indoline dye was 6.51%. Under the same conditions, the N3 dye was 7.89% and the N719 dye was 8.26%. The new indoline dye was optimized for the amount of 4-tert-butyl pyridine in the electrolyte and cholic acid as a coadsorbent. Subsequently, the solar energy to current conversion efficiencies reached 8.00%. This value was the highest obtained efficiency for dye-sensitized solar cells based on metal-free organic dyes without an antireflection layer.     

Dipolar organic pyridyl dyes for dye-sensitized solar cell applications

New dipolar dyes containing arylamine as the electron donor, 2-cyanoacrylic acid as the acceptor, and a conjugated spacer with incorporation of 2,5-pyridyl entity have been synthesized. Photophysical and electrochemical measurements, and theoretical computation were carried on these dyes. The solar cell devices using these dyes as the sensitizers exhibited light-to-electricity efficiencies in the range of 4.28–5.27%, which reaches 60–72% of N719-based device fabricated and measured under similar conditions. Better DSSC performance can be achieved with the dye where pyridine group is attached to thienyl or fluorenyl group because of favorable resonance energy and/or coplanarity for more effective charge transfer.     

Optimizing dyes for dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) have emerged as an important cheap photovoltaic technology. Charge separation is initiated at the dye, bound at the interface of an inorganic semiconductor and a hole-transport material. Careful design of the dye can minimize loss mechanisms and improve light harvesting. Mass application of DSSCs is currently limited by manufacturing complexity and long-term stability associated with the liquid redox electrolyte used in the most-efficient cells. In this Minireview, dye design is discussed in the context of novel alternatives to the standard liquid electrolyte. Rapid progress is being made in improving the efficiencies of such solid and quasi-solid DSSCs which promises cheap, efficient, and robust photovoltaic systems.     

Molecular engineering and theoretical investigation of organic sensitizers based on indoline dyes for quasi-solid state dye-sensitized solar cells

Novel indoline dyes, I-1-I-4, with structural modification of π-linker group in the D-π-A system have been synthesized and fully characterized. Molecular engineering through expanding the π-linker segment has been performed. The ground and excited state properties of the dyes have been studied by means of density functional theory (DFT) and time-dependent DFT (TD-DFT). Larger π-conjugation linkers would lead to broader spectral response and higher molar extinction coefficient but would decrease dye-loaded amount on TiO(2) electrode and LUMO level. While applied in DSSCs, the variation trends in short-circuit current density (J(sc)) and open-circuit voltage (V(oc)) were observed to be opposite to each other. The internal reasons were studied by experimental data and theoretical calculations in detail. Notably, I-2 showed comparable photocurrent values with liquid and quasi-solid state electrolyte, which suggested through molecular engineering of organic sensitizers the dilemma between optical absorption and charge diffusion lengths can be balanced well. Through studies of photophysical, electrochemical, and theoretical calculation results, the internal relations between chemical structure and efficiency have been revealed, which serve to enhance our knowledge regarding design and optimization of new sensitizers for quasi-solid state DSSCs, providing a powerful strategy for prediction of photovoltaic performances.     

Arylamine-based dyes for p-type dye-sensitized solar cells

New arylamine-based sensitizers for p-type dye-sensitized solar cells (DSSCs) have been synthesized and used for p-type DSSCs. The best conversion efficiency reaches ～0.1%. Sensitizers with two anchoring carboxylic acids lead to higher open-circuit voltages, short-circuit currents, and energy conversion efficiencies.     

Synthesis of triphenylamine-based thiophene-(N-aryl)pyrrole-thiophene dyes for dye-sensitized solar cell applications

Two new triphenylamine-based metal-free organic dyes (TPTDYE-1 and TPTDYE-2) containing 1-(2,6-diisopropylphenyl)-2,5-di(2-thienyl)pyrrole as a new π-conjugated chromophore were synthesized for dye-sensitized solar cell (DSSC) applications. TPTDYE-1 containing three donor groups around the acceptor group was found to show relatively narrow absorption band from 300 nm to 470 nm while TPTDYE-2 having extended π–π delocalization between the donor and acceptor group showed broad absorption band from 300 nm to 550 nm. The electrochemical studies indicate that the HOMO–LUMO energy gap of TPTDYE-1 is considerably wider than that of TPTDYE-2. The dye-sensitized solar cell performance of each dye was investigated, and the TPTDYE-2-sensitized cell was found to show a maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 75%, a short-circuit photocurrent density (J_sc) of 13.50 mA/cm², an open-circuit voltage (V_oc) of 0.72 V, and a fill factor (FF) of 0.69, corresponding to an overall conversion efficiency of 6.71% under simulated AM 1.5 irradiation (100 mW/cm²). Under the same condition the TPTDYE-1-sensitized cell showed the same IPCE value of 75% with a promising conversion efficiency of 6.00%, a J_sc of 11.11 mA/cm², a V_oc of 0.76 V, and a FF of 0.71.     

Design of NIR-absorbing simple asymmetric squaraine dyes carrying indoline moieties for use in dye-sensitized solar cells with Pt-free electrodes

Novel near-infrared (NIR)-sensitizing (up to 800 nm) simple asymmetric squaraine dyes (Sq 31 and Sq 33) carrying indoline moieties that did not require the introduction of any linker groups were developed. DSSCs fabricated with Sq 33 exhibited remarkable characteristics in the long-wavelength visible and NIR region (up to 800 nm), such as a conversion efficiency of 3.75% (AM 1.5G) with an incident photon-to-current conversion efficiency of 63% (650 nm), a short-circuit photocurrent density of 13.64 mA, an open-circuit photovoltage of 0.48, and a fill factor of 0.57.     

Organic dyes with a novel anchoring group for dye-sensitized solar cell applications

Two novel trialkylsilyl-containing organic sensitizers (JK-53 and JK-54) have been designed and synthesized. Nanocrystalline TiO₂–silica-based dye-sensitized solar cells (DSSCs) were fabricated using these dyes. Under standard global AM 1.5 solar conditions, the JK-53-sensitized cell gave a short-circuit photocurrent density (J_sc) of 6.37 mA cm^?2, an open-circuit voltage (V_oc) of 0.70 V, and a fill factor of 0.74. These values correspond to an overall conversion efficiency (η) of 3.31%. By comparison, the JK-54-sensitized cell resulted in a J_sc of 7.52 mA cm^?2, a V_oc of 0.71 V, and a fill factor of 0.75. These values give an overall conversion efficiency of 4.01%.     

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 characterization of three organic dyes with various donors and rhodanine ring acceptor for use in dye-sensitized solar cells

A series of new organic dyes comprising carbazole, iminodibenzyl, and phenothiazine moieties as the electron donors and rhodanine ring as the electron acceptor/anchoring groups were designed and developed for use in dye-sensitized solar cells. HOMO and LUMO energy level tuning was achieved by varying the carbazole, iminodibenzyls and phenothiazine donors. This was evidenced by spectral and electrochemical experiments and density functional theory calculations. Electrochemical studies indicated that the phenothiazine unit was much more effective in lowering the ionization potential than were the iminodibenzyl and carbazole units. The phenothiazine dye shows a solar-energy-to-electricity conversion efficiency (η) of 4.87%; the carbazole and iminodibenzyl dyes show η of 2.54% and 3.52%, respectively. These findings reveal that using carbazole, iminodibenzyl and phenothiazine donors as light-harvesting sensitizers are promising candidates for dye-sensitized solar cells.     

Highly-efficient metal-free organic dyes for dye-sensitized solar cells

A solar-to-electric conversion efficiency of 6.1% is achieved with this new dye, compared to 6.3% for N3 dye under the same experimental conditions. Although these indoline dyes are slightly less efficient than N3 dye, the cost of indoline dye is much less than for N3 due to ease of preparation. Furthermore, indoline dyes are shown to be highly stable to photoredox processes by cyclic voltammogram.     

Coplanar indenofluorene-based organic dyes for dye-sensitized solar cells

A series of new organic dyes, comprising indenofluorene moiety as a conjugated bridge, with an extended π-groups, such as thiophene and furan, diphenylamine as donor, cyanoacrylic acid group as an electron acceptor and anchoring group, have been synthesized. Photophysical and electrochemical measurements, and theoretical computation were carried out on these dyes. Dye-sensitized solar cells (DSSCs) using these dyes as the sensitizers exhibited photocurrent density (J_SC), open-circuit voltage (V_OC), and fill factor (FF) in the range of 6.95–8.20 mA/cm², 0.70–0.71 V, and 0.69–0.71, respectively, corresponding to an overall conversion efficiency of 3.36–4.05%. The best efficiency reached 56% of the standard cell based on N719.     

Novel organic dyes for efficient dye-sensitized solar cells

Two novel metal-free organic dyes containing thienothiophene and thiophene segments have been synthesized. Nano-crystalline TiO2 dye-sensitized solar cells were fabricated using these dyes as light-harvesting sensitizers, and a high solar energy-to-electricity conversion efficiency of 6.23% was achieved.     

New tetrazole-based organic dyes for dye-sensitized solar cells

A series of new metal-free organic dyes that contain donors with triphenylamine or its derivatives and tetrazole-based acceptors were synthesized and characterized by photophysical, electrochemical, and theoretical computational methods. They were applied in nanocrystalline TiO_2 solar cells(DSSCs). It is found that the introduction of diphenylamine units as antennas in the as-synthesized dyes could improve photovoltaic performance compared with phenothiazine and carbazole units as antennas in DSSCs. The dye with(2H-tetrazol-5-yl) acrylonitrile electron acceptor also displayed the highest solar-to-electrical energy conversion efficiency.     

Novel pyrenoimidazole-based organic dyes for dye-sensitized solar cells

A novel class of organic dyes containing pyrenoimidazole donors, cyanoacrylic acid acceptors, and oligothiophene π-linkers has been synthesized and characterized. The electro-optical properties of these dyes can be tuned by changing the conjugation length of the π-linkers. A dye containing terthiophene in the conjugation pathway exhibited a solar energy-to-electricity conversion efficiency of 5.65%.     

Oligothiophene-containing coumarin dyes for efficient dye-sensitized solar cells

We have developed oligothiophene-containing coumarin dyes fully functionalized for dye-sensitized nanocrystalline TiO(2) solar cells (DSSCs). DSSCs based on the dyes gave good performance in terms of incident photon-to-current conversion efficiency (IPCE) in the range of 400-800 nm. A solar energy-to-electricity conversion efficiency (eta) of 7.4% was obtained with a DSSC based on 2-cyano-3-[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)-[2,2']bithiophenyl-5-yl]acrylic acid (NKX-2677) under simulated AM 1.5G irradiation (100 mW cm(-2)) with a mask: short-circuit current density (J(sc)) = 13.5 mA cm(-2); open-circuit voltage (V(oc)) = 0.71 V; fill factor (FF) = 0.77. Transient absorption spectroscopy measurements indicated that electron injection from NKX-2677 to the conduction band of TiO(2) is very rapid (<100 fs), which is much faster than the emission lifetime of the dye (1.0 ns), giving a highly efficient electron injection yield of near unity.     

Novel polyene dyes for highly efficient dye-sensitized solar cells

We have developed an efficient and novel polyene-dye-sensitized nanocrystalline TiO2 solar cells producing a 6.8% solar energy-to-electricity conversion efficiency (eta) under AM 1.5 irradiation (100 mW cm(-2)): short-circuit current density (Jsc), 12.9 mA cm(-2), open-circuit photovoltage (Voc), 0.71 V, fill factor (ff), 0.74.