Molecular Engineering of Efficient Organic Sensitizers Containing Diyne-Bridge for Dye-Sensitized Solar Cells

Fused diethynylbenzenes and phenanthrenes via arynes with alkynylsilanes

A method for the hydroalkynylation and catalytic cyclization reactions of hexadehydro-Diels-Alder-derived benzynes is described. Diethynylbenzene derivatives are generated in a one-step reaction via trimethylsilyl-alkyne groups with benzyne formed by heating the appropriate tetrayne substrate. Trimethyl(phenylethynyl)silane loses TMS and binds to the electron-deficient site on HDDA-derived benzynes, and then phenanthrene was synthesized under mild reaction conditions by transition-metal-free, base promoted intramolecular cyclization.

Novel Red Light-Absorbing Organic Dyes Based on Indolo[3,2-b]carbazole as the Donor Applied in Co-Sensitizer-Free Dye-Sensitized Solar Cells

Three novel organic dyes (D6, D7 and D8), based on indolo[3,2-b]carbazole as the donor and different types of electron-withdrawing groups as the acceptors, were synthesized and successfully applied in dye-sensitized solar cells (DSSCs). Their molecular structures were fully characterized by ¹H NMR, ¹³C NMR and mass spectroscopy. The density functional theory (DFT) calculations, electrochemical impedance spectroscopy analysis, UV–Vis absorption characterization and tests of the solar cells were used to investigate the photophysical/electrochemical properties as well as DSSCs’ performances based on the dyes. Dye D8 showed the broadest light-response range (300–770 nm) in the incident monochromatic photo-to-electron conversion efficiency (IPCE) curve, due to its narrow bandgap (1.95 eV). However, dye D6 exhibited the best device performance among the three dyes, with power conversion efficiency of 5.41%, J_sc of 12.55 mA cm⁻², V_oc of 745 mV and fill factor (FF) of 0.59. We also found that dye aggregation was efficiently suppressed by the introduction of alkylated indolo[3,2-b]carbazole, and, hence, better power conversion efficiencies were observed for all the three dyes, compared to the devices of co-sensitization with chenodeoxycholic acid (CDCA). It was unnecessary to add adsorbents to suppress the dye aggregation.

Aggregation-Free Organic Dyes Featuring Spiro[dibenzo[3,4:6,7]cyclohepta[1,2-b]quinoxaline-10,9'-fluorene] (SDBQX) for Dye-Sensitized Solar Cells

Three novel organic dyes coded as FHD4-1, FHD4-2, and FHD4-3 featuring spiro[dibenzo[3,4:6,7]cyclohepta[1,2-b]quinoxaline-10,9'-fluorene] (SDBQX) moieties are designed to inhibit dye aggregation to improve the performance of dye-sensitized solar cells (DSSCs). The consistent absorption onsets of FHD4-1, FHD4-2, and FHD4-3 in solutions and adsorbed on TiO2 films indicate that these dyes are aggregation-free dyes. Therefore, coadsorption with chenodeoxycholic acid (CDCA) of these three dyes reduces the performance of DSSCs because no inhibition effect for dye aggregation is needed, but, on the contrary, the dye loading amount is reduced after addition of CDCA.