Hidetoshi Miura

High-conversion-efficiency organic dye-sensitized solar cells with a novel indoline dye

An indoline dye (D205), the synthesis method of which is disclosed in this report, gave high-efficiency organic dye-sensitized solar cells (9.52%) using an anti-aggregation reagent (chenodeoxycholic acid).

APPLICATION OF HIGHLY ORDERED TIO2 NANOTUBE ARRAYS IN FLEXIBLE DYE- SENSITIZED SOLAR CELLS

TiO(2) nanotube arrays prepared by electrochemical anodization of Ti foils show impressive light to electricity conversion efficiency in the dye-sensitized solar cells (DSCs). The length of the TiO(2) nanotube arrays (5-14 microm) was controlled by varying the anodization time from 2 to 20 h. The influence of nanotube lengths on the photovoltaic performance of DSCs was investigated by impedance. A flexible DSC using TiO(2) nanotube arrays on a Ti foil as a working electrode and polyethylene naphthalate (ITO/PEN) as counterelectrode in combination with solvent-free ionic liquid electrolyte achieved 3.6% photovoltaic conversion efficiency under simulated AM 1.5 sunlight.

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.

Novel thiophene -conjugated indoline dyes for zinc oxide solar cells

The application of a series of thiophene-conjugated indoline dyes for zinc oxide solar cells, prepared by the one-step cathode deposition template method, was examined. The introduction of thiophene ring(s) into D131-type indoline dye improved the cell performance due to their appropriate energy levels and bathochromic shift in the UV-vis absorption band on zinc oxide. It is important for the oxidation potential (Eox) of dyes to have a more positive value than ca. 0.25 V vs. Fc/Fc+ in acetonitrile in order to show a high (>70%) incident photon-to-current efficiency.

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 containing fluorene-substituted indoline core for zinc oxide dye-sensitized solar cell

A novel idoline dye, having dimethylfluorene-substituted indoline donor and dicyanovinylidene-introduced rhodanine acceptor (DN350), gave much higher efficiency than D205 due to bathochromic absorption band and prevention of aggregates formation.

Stable Sensitization of ZnO by Improved Anchoring of Indoline Dyes

To establish photovoltaics on a large scale of terawatts (TW), following scenarios of a sustainable energy supply based on renewable sources while avoiding large contributions to CO2 emission by burning of fossil fuels, technologies are needed that are based on abundant elements and that have a small energy payback time. Dyesensitized solar cells (DSCs) have the potential to fulfil these conditions since they consist of either TiO2 or ZnO, which are abundant in the earth crust. Energy payback times of 0.6–0.8 years were calculated for cells based on TiO2, [5] well comparable to the 0.8 years of presentday record CdTe cells. DSCs based on ZnO as semiconductor instead of TiO2 provide further potential to reduce this time because they can be electrodeposited from aqueous electrolytes without additional annealing steps and therefore allow cell preparation based on light-weight, low-energy polymer substrates. For ZnO, however, the classical established dyes, such as substituted Ru-trisbypyridine complexes, are chemically too aggressive and new sensitizer molecules have to be established. 7] Among the dyes tested as sensitizers for ZnO, an indoline dye (D149) has proven to reach the highest efficiencies in such cells (5.6 %). However, D149 is not stably fixed at the ZnO surface but is dissolved from the electrode when in contact to standard electrolytes. Herein, we study differently substituted indoline dyes with additional carboxylate anchoring groups. We show that these dyes (Scheme 1) strongly bind to the ZnO surface and that the stability of the cells can be increased while maintaining their efficiency. For our experiments, we used fluorine-doped tin oxide (FTO) films on glass onto which we first deposited a compact ZnO blocking layer (~1 mm) by polarizing the electrode at 1.06 V (vs. Ag/AgCl) in an O2-saturated aqueous solution of ZnCl2 (5 mm) with KCl (0.1 m) as supporting electrolyte for 10 min. Following this, eosin Y (50 mm) was added as a structure-directing agent and a porous ZnO layer was deposited at 0.96 V (vs. Ag/AgCl) for 20 min; eosin was then removed in a pH 10.5 KOH solution. The dyes D149, DN216 or DN285 were then adsorbed from 0.5 mm solutions in acetonitrile/tert. butanol (1:1 by vol.) at room temperature for 10 min. To obtain a measure of the energetic position of the electron in the excited state of the sensitizer, we measured the redox potentials of the molecules dissolved in dimethylformamide (DMF). The potential of the first reduction was used as a measure of the LUMO (lowest unoccupied molecular orbital) energy which further is assumed to be characteristic for the energy of an electron in the first excited singlet state. Figure 1 a shows the results of cyclic voltammetry (CV) measured at a Pt sheet in contact with the dye solutions. Beyond an inert potential window ( 0.3 V to + 0.7 V), clear waves were observed for the reduction and oxidation of the molecules. The redox characteristics of DN216 and DN285 to a large extent resembled those of D149. To obtain a safe assignment of the observed waves to changes in the HOMO (highest occupied molecular orbital) or LUMO population of the chromophore system (Table 1), which is decisive for the injection characteristics of a sensitizer, spectroelectrochemcial experiments were performed (Figures 2 and 3). The spectra were measured at constant potentials subsequent to a peak in the CV to obtain a sufficiently large signal (Figure 1 a). The absorption of the sensitizers measured in DMF (Figure 1 b) showed a peak maximum at 392 nm, assigned to a p!p* transition, and the main peak of internal charge transfer in the visible range at lmax = 534 nm, which is observed for all dyes independently of substitution. The extinction coefficient was determined to be e= 46700, 77600 and

The baeyer-villiger reaction of strained cage compounds, 1,3-bishomocubanones, via carbocations

Abstract The Baeyer-Villiger oxidation of 1,3-bishomocubanone 1a in chloroform with m-chloroperbenzoic acid (m-CPBA) at room temperature proceeds quite rapidly and gives the ordinary lactone, 10-oxapentacy-clo[5.4.0.02.5.03.9.04.8]undecan-11-one 2a and the skeletal rearrangement product, 11-oxapentacy-clo[6.3.0.02.4.03.7.05.9]undecan-10-one 4a. Methyl substituted homologs (1d, 1e, 1f) of 1a give the corresponding ordinary and rearranged lactones (2d, 2e, 2f, 4d, 4e, 4f). In these oxidations, the mechanism via carbocations, cyclobutyl 18 and cyclopropylcarbinyl cations 19, plays a major role different from the ordinary concerted migration mechanism. Solvent effects, kinetic treatments, and methyl substituent effects on product ratios support this carbocation mechanism. The adduct formation process between a ketone and m-CPBA must be rate-determining.

Modification of α-santonin VI. Synthesis of (+)-deoxyvernolepin

Abstract (+)-Deoxyvernolepin is synthesized from α-santonin via angular methyl activation and subsequent furan ring opening.

Importance of fluorescence lifetimes for efficient indoline dyes in dye-sensitized solar cells

To make a molecular design of efficient indoline dyes, fluorescence lifetimes should be longer than ca. 0.8 ns in chloroform, in addition to suitable HOMO and LUMO levels and bathochromic UV-vis absorption bands.