Effect of triptycene unit on the performance of porphyrin-based dye-sensitized solar cells

Sensitizers of Metal Complexes with Sulfur Coordination Achieving a Power Conversion Efficiency of 12.89

In the study to improve the light absorption range and intensity of dye sensitizers in the visible region and promote their photovoltaic performance, five novel polymeric metal complexes with sulfur coordination (BDTT-VBT-Ni, BDTT-VBT-Cu, BDTT-VBT-Zn, BDTT-VBT-Cd, and BDTT-VBT-Hg) to be used as D-A-π-A motif dye sensitizers were designed, synthesized, and characterized. In these polymeric metal complexes with sulfur coordination, the metal complexes with sulfur coordination of benzodithiophene derivatives are used as auxiliary electron acceptors, 8-quinolinol derivatives are used as π-bridge and electron acceptors, and thienylbenzene-[1,2-b:4,5-b'] dithiophene (BDTT) are used as electron donors. The effect of different metal complexes with sulfur coordination on the photovoltaic performance of dye sensitizers has been systematically studied. Under AM 1.5 irradiation (100 mW cm^-2), the devices of dye-sensitized solar cells (DSSCs) based on five polymeric metal complexes with sulfur coordination exhibited a short-circuit current density (J_sc) of 13.43, 15.07, 18.00, 18.99, and 20.78 mA cm^-2, respectively, and their power conversion efficiencies (PCEs) were 7.10, 8.59, 10.68, 11.23, and 12.89%, respectively, and their thermal decomposition temperatures (T_d) were 251, 257, 265, 276, and 277 °C, respectively. The result shows that the J_sc and PCE of five polymeric metal complexes increase by degrees, and the PCE of BDTT-VBT-Hg is up to 12.89%, which is because of the strength of the coordination bonds between Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) and sulfur increases in turn so that the electron-withdrawing ability and electron-transfer ability of auxiliary electron acceptors is enhanced. These results provide a new way to develop stable and efficient metal complexes with sulfur coordination dye sensitizers in the future.

Spectral properties and photophysical processes of meso styryl substituent triphenylamine-porphyrin derivatives

This work reports the synthesis and spectral properties of meso-styryl substituted triphenylamine-porphyrin derivatives, mP-BLP, mPPC-BLP and their metal coordinated complexes. The photophysical processes were analyzed and related to the meso-groups and centre metal ions. The meso styryl substituent in mP-BLP and its complexes are able to extend the conjugation of porphyrin macrocycle to the styryl motif, increase light harvesting ability and accelerate intersystem crossing (ISC) process. A large dihedral angle between the meso-styryl group and porphyrin macrocycle would prohibit the delocalization of electrons between the two motifs and induce the occurrence of solvation decay process. Increasing the electron-withdrawing ability of meso-substituent via additional pyrimidine group could promote the photoinduced intramolecular electron transfer (PIET) process for mPPC-BLP. Moreover, the coordination of metal ions would significantly accelerate the photophysical processes of both mP-BLP and mPPC-BLP. Specially, the Mg[Formula: see text] is helpful to the ISC process whereas Zn[Formula: see text] is adverse to the ISC process, while Cu[Formula: see text] would boost the non-radiation process. Furthermore, Zn[Formula: see text] is able to promote the PIET process of mPPC-BLP, exhibiting the highest charge-separated tendency among these porphyrins. mPPC-ZnBLP-based dye-sensitized solar cell (DSSC) devices show the highest power conversion efficiency (PCE). The photovoltaic performance of DSSC devices reveals the significancy of the photoinduced charge-separated tendency for the design of porphyrin sensitizers.