Synthesis of asymmetric zinc phthalocyanine with bulky diphenylthiophenol substituents and its photovoltaic performance for dye-sensitized solar cells

Effect of the Number of Anchoring and Electron-Donating Groups on the Efficiency of Free-Base- and Zn-Porphyrin-Sensitized Solar Cells

A series of porphyrin compounds, free base (H₂P) and their Zn (II) metallated analogues (ZnP), bearing one, two or three carboxylic acid groups, have been synthesized, characterized, and used as sensitizers in dye sensitized solar cells (DSSCs). The performance of these devices has been analyzed, showing higher efficiencies of those sensitized with ZnP compounds. These results have been explained, on one hand, taking into account the electronic character of the metal ion, which acts as mediator in the injection step, and, on the other, considering the number of anchoring groups, which determines both the stereoelectronic character of the dye and the way it binds to TiO₂ surface.

Near-Infrared-Absorbing Metal-Free Organic, Porphyrin, and Phthalocyanine Sensitizers for Panchromatic Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSCs) are a promising source of renewable energy. However, the power conversion efficiency (PCE) of devices has been limited largely by the difficulty of producing electricity using photons from the near-infrared (NIR) spectral region. Metal-free organic sensitizers frequently employ strong electron-donating or -withdrawing moieties to tune the optical band gap to allow the absorption of lower energy wavelengths in charge-transfer systems, whereas porphyrins and phthalocyanines use substituents to shift the Soret and Q bands toward lower energy absorption. Very few devices employing precious metal-free dyes have achieved panchromatic and NIR photon conversion for electricity generation at wavelengths >750 nm despite a tremendous number of sensitizers published over the last 25 years. This Minireview seeks to compile a summary of these sensitizers to encourage assimilation, analysis, and development of efficient future sensitizers with absorption extending into the NIR. Herein, we discuss common synthetic strategies, optical properties, and electronic properties of the most successful panchromatic organic sensitizers.

Discotic liquid crystals of transition metal complexes, 53†: synthesis and mesomorphism of phthalocyanines substituted by m-alkoxyphenylthio groups

We have successfully synthesized a series of novel octakis([Formula: see text]-alkoxyphenylthio)phthalocyaninato copper(II) complexes, ([Formula: see text]-C[Formula: see text]OPhS)[Formula: see text]PcCu ([Formula: see text] = 2, 4, 6, 8, 10, 12, 14, 16: 1b~1i), by our developed method to reveal their mesomorphism. The phase transition behavior and mesophase structures have been established by using a polarizing optical microscope, a differential scanning calorimeter, and a temperature-dependent small angle X-ray diffractometer. Interestingly, the very short chain-substituted derivatives, ([Formula: see text]-C[Formula: see text]OPhS)[Formula: see text]PcCu (1a) and ([Formula: see text]-C[Formula: see text]OPhS)[Formula: see text]PCu (1b), show a hexagonal ordered columnar (Col[Formula: see text] mesophase, whereas each of the other longer-chain-substituted derivatives, ([Formula: see text]-C[Formula: see text]OPhS)[Formula: see text]PcCu ([Formula: see text] = 4~16: 1c~1i), shows only rectangular ordered columnar (Col[Formula: see text] mesophase(s). In contrast to the present longer-chain-substituted phenylthio derivatives, each of the previous longer-chain-substituted phenoxy derivatives, ([Formula: see text]-C[Formula: see text]OPhO)[Formula: see text]PcCu ([Formula: see text] = 10–20), shows a different columnar mesophase of Col[Formula: see text]. We discuss this difference of mesomorphism from the viewpoint of the different steric hindrance originated by the peripheral substituents, PhO and PhS groups. Moreover, we could estimate the optical band gaps of ([Formula: see text]-C[Formula: see text]OPhO)[Formula: see text]PcCu and ([Formula: see text]-C[Formula: see text]OPhS)[Formula: see text]PcCu (1f) from absorption edge of the Q-bands to be 1.79 eV and 1.70 eV, respectively. Therefore, the phenylthio-substituted derivative gave a narrower band gap byca. 0.1 eV in comparison with the phenoxy-substituted derivative.