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Abstract: Four donor–conjugated spacer–acceptor (D–π–A) organic dyes containing cyclopentadithiophene unit as a part of the conjugated spacer are prepared and studied to investigate the effects of the conjugated spacer and donor on the short-circuit current and conversion efficiency of the corresponding DSSCs. Theoretical calculations reveal that a shorter conjugated spacer or a stronger donor leads to more effective electron injection upon photo excitation. Therefore, D–π–A typed dye with longer conjugated spacer may have higher absorption coefficient and longer λ max. Nevertheless, it may also have lower effective electron injection upon photo excitation. Calculation data also show that cyclopentadithiophene although is a good moiety for extending the conjugation length of the organic dyes, it also acts as an electron sink, decreasing the effective electron injection. The transition probability calculated with the electron density difference analyses combining with the experimental absorption and photovoltaic performance data provides a useful protocol for designing organic photosensitizers for DSSCs at the electronic and structural levels. [Copyright &y& Elsevier]

Five monochloro- s -triazinyl reactive dyes (MCT) and five m -carboxypyridium- s -triazinyl reactive dyes (NTR) were synthesised with the same red chromophore bearing an –NHCN, –OCH 3 , –CH 3 NSO 2 CH 3 , – N -methyl phenyl or –OH group as 'second-leg' substituents. A kinetic study of the hydrolysis of these dyes was conducted, and the rate constant (k obs) and half-life time values were determined. The k obs of the MCT and NTR dyes was found to follow the order –OCH 3 > –CH 3 NSO 2 CH 3 > – N -methyl phenyl > –NHCN > –OH, which was approximately in agreement with the values obtained for the Hammett substituent constants. Overall, the higher the electron-donating property of the substituent on meta -position to the leaving group in the triazine ring, the lower the hydrolysis rate constant. • Chloro substituent in the MCT dyes was replaced by nicotinic acid, the reactivity was enhanced. • The order of reactivity of dyes is related to the electronic effect of the substituent. • The order of k obs was in agreement with the values of Hammett substituent constants. [ABSTRACT FROM AUTHOR]

Two diketopyrrolopyrrole (DPP) containing D–π–A organic dyes, named as TEDBn and TEDTh were prepared. Their optical, electrochemical and photophysical properties were investigated and their application in dye-sensitized solar cells (DSCs) was demonstrated. The broaden absorption and low-energy λ max of DPP containing dyes were contributed from DPP bridge and EDOT π-conjugated moiety. Compared to TEDTh, TEDBn has smaller absorption coefficient and higher optical bandgap. Nevertheless the power conversion efficiency (PCE) of TEDBn based DSC is 7.2% which is larger than that of TEDTh based DSC and 90% of N719 based cell. The higher PCE of TEDBn based device originates from both higher open-circuit voltage (V OC ) and short-circuit current (J SC ). Femtosecond time-resolved photoluminescence data show that the electron injection at TEDBn/TiO 2 is more efficient than that at TEDTh/TiO 2 interface, resulting in higher J SC (and IPCE) of TEDBn based DSC. Density function theory (DFT) calculations revealed that TEDBn is a linear structure which leads to higher dye loading on TiO 2 than TEDTh which featured a bend conformation, better TiO 2 surface coverage, resulting in larger V OC . Therefore, the overall efficiency of the cell sensitized by TEDBn is better than that the devices based on TEDTh. [ABSTRACT FROM AUTHOR]

Abstract: A novel, heteroleptic ruthenium dye comprising a vinyl group between the carboxylate and bipyridine segments as well as extended π-conjugation of the ancillary ligand, employing alkyl-bithiophene, was synthesized. The dye displayed a remarkably high absorption coefficient of 2.51 × 104 M−1 cm−1 (at 562 nm) for its metal-to-ligand charge transfer band. The photo-to-current conversion efficiency of the corresponding dye-sensitized solar cell was 9.12% under AM 1.5 (100 mW/cm2) irradiation. Furthermore, owing to both the very strong metal-to-ligand charge transfer band and the large number of dye molecules adsorbed on the TiO2 electrode, the conversion efficiency of the dye-sensitized cell was >7.5% at a light intensity ≤198 mW cm−2. [Copyright &y& Elsevier]