Pyridine derivatives; new efficient additives in bromide/tribromide electrolyte for dye sensitized solar cells

RSC Advances Pub Date: 2015-10-12 DOI: 10.1039/C5RA15894J

Abstract

In this work, two new inexpensive pyridine derivatives, propyl isonicotinate (PIN) and isopropyl isonicotinate (IPIN), have been synthesized through a simple and low cost method and for the first time, they have been applied as effective additives in bromide/tribromide electrolyte in dye sensitized solar cells (DSSCs). Although the iodide/triiodide redox shuttle shows remarkable performance in DSSCs, but bromide/tribromide couple has a more positive redox potential in comparison to this couple. Therefore, it is good idea to design dyes whose HOMO and LUMO levels match with the redox potential of bromide/tribromide and the conduction band (CB) of TiO2, respectively. We have synthesized 3-(4-carbazole-9-yl-phenyl)-2-cyano-acrylic acid (TC301) and 2-cyano-3-(4-(3,6-di-tert-butyl-9H-carbazole-9-yl)phenyl) acrylic acid (TC302) as two carbazole dyes and applied them with modified electrolyte in DSSCs. The influence of PIN and IPIN additives in bromide/tribromide redox electrolyte on the DSSC performances is investigated. In comparison to electrolyte without additive, adding 0.5 M of these additives to the electrolyte solution leads to an increase in the open circuit voltage (Voc) and short current density (Jsc), consequently the energy conversion efficiency (η) improves. Electrochemical impedance spectroscopy show that the enhancement in Voc is due to increasing electron density in the CB of TiO2 so that a shift in the Fermi level (EF) occurs. It leads to a suppression in electron recombination that has beneficial effect on the Voc. Furthermore, cyclic voltammetry results reveal that PIN and IPIN has similar effect mechanisms to 4-tert-butylpyridine (TBP) additive in the DSSCs. Our findings show that TBP can be replaced with PIN and IPIN in the DSSCs.

Graphical abstract: Pyridine derivatives; new efficient additives in bromide/tribromide electrolyte for dye sensitized solar cells
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