Triazoloisoquinoline-based dual functional dyestuff for dye-sensitized solar cells

Triazoloisoquinoline contains electron-rich nitrogen and oxygen heteroatoms in a heterocyclic structure with high electron-donating ability. By utilizing this feature, two organic dyesutffs containing triazoloisoquinoline were synthesized and used in the fabrication of dye-sensitized solar cells (DSSCs), overcoming the deficiency of ruthenium dyestuff absorption in the blue part of the visible spectrum. This method also fills the blanks of ruthenium dyestuff sensitized TiO2 film, and forms a compact insulating molecular layer due to the nature of small molecular organic dyestuffs. The incident photon-to-electron conversion efficiency of N719 at shorter wavelength regions is 35%. After addition of triazoloisoquinoline-based dyestuff for co-sensitization, the IPCE at 350–500 nm increased significantly. This can be attributed to the increased photocurrent of the cells, which improves the dye-sensitized photoelectric conversion efficiency from 4.49% to 5.15%, which the overall conversion efficiency increased by about 15%. As a consequence, this low molecular weight organic dyestuff is a promising candidate as co-adsorbent and co-sensitizer for highly efficient dye-sensitized solar cells.

They consist of treating triazoloisoquinolines substituted tetramethyl-dioxaborolane (2) with 5-formyl-2-bromothiophene under conditions for Suzuki coupling to produce 5-(4-(3-oxo-[1,2,4]triazolo[3,4-a]isoquinolin-2(3H)-yl)phenyl)thiophene-2-carbaldehyde (3). Knoevenagel condensation of compound 3 with cyanoacrylic acid is carried out in the presence of piperidine, and after precipitation and purification with silica gel chromatography, the final dyestuff 4L is obtained as a yellow powder. This product has been characterized by spectroscopic analyses.Figure optionsDownload as PowerPoint slideHighlights
► This new dyestuff investigated the role of triazoloisoquinoline dyestuffs as co-adsorbents and co-sensitizers with N719.
► The results show that co-adsorption of N719 sensitizer with dyestuff 5 increases the photocurrent in 1–0.25 molar ratio.
► This improved conversion efficiency is attributed to the insulating molecular layer, and the light harvesting effect at shorter-wavelength regions.