Metal-free dyes (BP-1 to BP-3) containing a 9,10-dihydrophenanthrene unit in the spacer have been synthesized. The dye with the highest cell efficiency, BP-2, was used in combination with SQ2 for cosensitized DSSCs. The cosensitized DSSC in which the ratio of BP-2 and SQ2 is 8:2 (v/v) has a record high efficiency of 8.14% among cosensitized systems using all metal-free sensitizers. Dye distribution along the TiO(2) film depth was analyzed by an Auger electron spectroscopy technique.

New dipolar compounds incorporating a dithieno[3,2-b:2',3'-d]thiophene unit as the electron donor, an oligothiophene moiety as the conjugated spacer, and 2-cyanoacrylic acid as the electron acceptor have been synthesized. These nonarylamine type metal-free organic compounds have been successfully used as the sensitizers of dye-sensitized solar cells (DSSCs). The conversion efficiencies of the DSSCs range from 3.54 to 5.15% under AM 1.5 G irradiation. The best efficiency reached approximately 70% of the ruthenium dye N719-based standard cell fabricated and measured under similar conditions.

New metal-free dyes with a furan moiety in the conjugated spacer between the arylamine donor and the 2-cyanoacrylic acid acceptor have been synthesized, and high efficiency dye-sensitized solar cells were fabricated using these molecules as light-harvesting sensitizers.

Dye-sensitized solar cells using nanocrystalline ZnO as the photoanode and a metal-free sensitizer with a benzothiadiazole entity directly connected to the 2-cyanoacrylic acid acceptor exhibited an efficiency (5.18%) higher than those using the TiO(2) photoanode. Use of a hierarchical ZnO back scattering layer further improved the efficiency to 5.82%.

New near-IR (NIR) squaraine dyes (p-SQ1 and p-SQ2) containing one and two anchoring groups were synthesized and used as the sensitizers of p-type DSSCs. The dye (0.113%) with two anchoring groups (p-SQ2) shows better performance than the dye (0.053%) with only one anchoring group (p-SQ1). Cosensitized p-type DSSCs using two dyes with complementary absorption were tested. They have broadened IPCE spectra and good cell performance.

Small molecule BODIPY dyes incorporating conjugated substituents at the β sites have been synthesized. Solution processed inverted bulk heterojunction cells were fabricated from the blends of the dyes and PC(71)BM. The cells exhibited very high open-circuit voltages (>0.9 V) and a high conversion efficiency of 3.22% has been achieved.

New dipolar sensitizers containing an ethyl thieno[3,4-b]thiophene-2-carboxylate (ETTC) entity in the conjugated spacer have been synthesized in two isomeric forms. These compounds were used as the sensitizers of n-type dye-sensitized solar cells (DSSCs). The best conversion efficiency (5.31%) reaches approximately 70% of the N719-based (7.41%) DSSC fabricated and measured under similar conditions. The ETTC-containing compounds exhibit a bathochromic shift of the absorption compared to their thiophene congeners due to the quinoid effect, however, charge-trapping at the ester group of ETTC was found to jeopardize the electron injection and lower the cell efficiency. Charge trapping is alleviated as the ester group of ETTC is replaced with a hydrogen atom, as evidenced from the theoretical computation.

A series of new organic dyes, comprising a naphthyl moiety as a π-conjugated bridge, different amines as donors, and a cyanoacrylic acid group as an electron acceptor and anchoring group, have been designed and synthesized for applications in dye-sensitized solar cells (DSSCs). One of the compounds was also characterized by single-crystal X-ray structural analysis. All of the dyes exhibited maximum absorptions in the range of 371-441 nm. The short-circuit photocurrent density, open-circuit voltage, and fill factor (FF) values of the devices are in the range of 6.13-10.90 mA cm(-2), 0.62-0.69 V, and 0.62-0.67, respectively, corresponding to an overall conversion efficiency of 2.76-4.55%. The conversion efficiency reached 38-62% of that of a N719-based device (7.31%) fabricated and measured under similar conditions. Steric congestion between the naphthyl and aromatic moieties jeopardizes charge transfer from the donor to the acceptor. Insertion of an alkenyl entity between the naphthyl entity and the aromatic ring alleviates steric congestion and leads to longer wavelength electronic absorption spectra.

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.

A novel series of dipolar organic dyes containing diarylamine as the electron donor, 2-cyanoacrylic acid as the electron acceptor, and fluorene and a heteroaromatic ring as the conjugating bridge have been developed and characterized. These metal-free dyes exhibited very high molar extinction coefficients in the electronic absorption spectra and have been successfully fabricated as efficient nanocrystalline TiO(2) dye-sensitized solar cells (DSSCs). The solar-energy-to-electricity conversion efficiencies of DSSCs ranged from 4.92 to 6.88 %, which reached 68-96 % of a standard device of N719 fabricated and measured under the same conditions. With a TiO(2) film thickness of 6 mum, DSSCs based on these dyes had photocurrents surpassing that of the N719-based device. DFT computation results on these dyes also provide detailed structural information in connection with their high cell performance.

The new sensitizer MC119 has been synthesized and the solar cell constructed with 0.25 cm(2) active area photoelectrode in combination with an electrolyte composed of 0.6 M dimethylpropyl-imidazolium iodide (DMPII), 0.05 M I(2), 0.5 M TBP and 0.1 M LiI in acetonitrile achieved a solar to electric energy conversion efficiency (η) of 8.36% under Air Mass (AM) 1.5 sunlight, while the reference N719 sensitized solar cell exhibited η-value of 7.2%.

Efficient light harvesting: Cyclometalated ruthenium complexes were synthesized and evaluated in a dye-sensitized solar cell as near-IR sensitizers. Tuning of the HOMO energy level by structural modifications of the ligand improved the conversion efficiency of the cells based on these complexes to up to 10.7 %.

New dipolar sensitizers containing an ethyl thieno[3,4-b]thiophene-2-carboxylate (ETTC) entity in the conjugated spacer have been synthesized in two isomeric forms. These compounds were used as the sensitizers of n-type dye-sensitized solar cells (DSSCs). The best conversion efficiency (5.31%) reaches approximately 70% of the N719-based (7.41%) DSSC fabricated and measured under similar conditions. The ETTC-containing compounds exhibit a bathochromic shift of the absorption compared to their thiophene congeners due to the quinoid effect, however, charge-trapping at the ester group of ETTC was found to jeopardize the electron injection and lower the cell efficiency. Charge trapping is alleviated as the ester group of ETTC is replaced with a hydrogen atom, as evidenced from the theoretical computation.

Phenothiazinyl rhodanylidene acetic acid merocyanine dyes with variable substitution pattern on the peripheral benzene ring were synthesized in good to excellent yields by Knoevenagel condensation of the corresponding phenothiazinyl aldehydes and rhodanine-N-acetic acid. The electronic properties were investigated by cyclic voltammetry, absorption, and fluorescence spectroscopy. Electron releasing substitution leads to an appreciable lowering of the oxidation potential, bathochromic shift of the absorption band, and minimization of the emission quantum yield. Not least as a consequence of these properties, the compounds are interesting for use as chromophores in dye-sensitized solar cells (DSSC). DSSCs were constructed and successfully tested by determining the characteristic parameters such as incident-photon-to-electron conversion efficiency (IPCE), fill factor (FF), and overall efficiency.

A new class of cyclometalated ruthenium sensitizers incorporating a ĈNN ligand and conjugated 2,2'-bipyridine in the ancillary ligand have been designed and synthesized. The photovoltaic performance of JK-206 using an electrolyte containing 0.6 M 1,2-dimethyl-3-propylimidazolium iodide, 0.05 M I(2), 0.1 M LiI, and 0.5 M tert-butylpyridine in CH(3)CN gave a short-circuit photocurrent density of 19.63 mA cm(-2), an open-circuit voltage of 0.74 V, and a fill factor of 0.72, affording an overall conversion efficiency of 10.39%. The efficiency is the highest one reported for dye-sensitized solar cells based on the cyclometalated ruthenium sensitizer of the type ĈNN. Moreover, the same device using a polymer gel electrolyte exhibited a remarkable stability under 1000 h of light soaking at 60 °C, retaining 91% of the initial efficiency of 7.14%.

A series of new organic dyes exploiting coplanar indacenodithiophene as the central π-spacer of the classical donor-(π-spacer)-acceptor configuration were synthesized and characterized for dye-sensitized solar cells. The coplanarity of the indacenodithiophene core facilitates efficient donor to acceptor charge transfer, imparting the new organic dyes significant bathochromic shifts and remarkable power conversion efficiencies of up to 6.7%(DTInDT) under AM 1.5G radiation.

A new class of organic sensitizers incorporating a benzo[1,2-b:4,5-b']dithiophene (BDT) unit as conjugated spacer has been synthesized and successfully used for dye-sensitized solar cells (DSSCs). The length of the π-conjugated spacers has a strong impact on electro-optical properties of these dyes, leading to the conversion efficiencies ranging from 4.17 to 5.68% under AM 1.5 G irradiation. This result indicates that the BDT unit is a promising candidate in organic sensitizers.

A novel multifunctional conjugated polymer (RCP-1) composed of an electron-donating backbone (carbazole) and an electron-accepting side chain (cyanoacetic acid) connected through conjugated vinylene and terthiophene has been synthesized and tested as a photosensitizer in two major molecule-based solar cells, namely dye sensitized solar cells (DSSCs) and organic photovoltaic cells (OPVs). Promising initial results on overall power conversion efficiencies of 4.11% and 1.04% are obtained from the basic structure of DSSCs and OPVs based on RCP-1, respectively. The well-defined donor (D)-acceptor (A) structure of RCP-1 has made it possible, for the first time, to reach over 4% of power conversion efficiency in DSSCs with an organic polymer sensitizer and good operation stability.

A novel efficient metal free sensitizer containing asymmetric double donor-π-acceptor chains (DC) was synthesized for dye-sensitized solar cells (DSSCs). Comparing to 3.80%, 4.40% and 4.64% for the DSSCs based on the dyes with single chain (SC1, SC2) and cosensitizers (SC1 + SC2), the overall conversion efficiency reaches 6.06% for DC-sensitized solar cells as a result of its longer electron lifetime and higher incident monochromatic photon-to-current conversion efficiency.

Ru(II) heteroleptic complexes as photosensitizers for dye-sensitized solar cells (DSCs) are presented. The article outlines design strategies, synthetic routes, optical and photovoltaic properties of ruthenium dyes based on polypyridines as ancillary ligands containing π-conjugated electron-rich heteroaromatic groups. The integration of donor heteroaromatic substituents, typically thiophene-based moieties, strongly improves the optical properties of the sensitizers in terms of bathochromic and hyperchromic shift compared to prototypical dyes N3 and N719. These favorable properties in turn yield DSCs with superior light harvesting abilities, higher external quantum efficiencies, improved device photocurrents, and top-ranked power conversion efficiencies. In combination with excellent stabilities under thermal stress and light soaking, this class of DSC photosensitizer has great potential for practical applications.