Effects of triphenyl phosphate as an inexpensive additive on the photovoltaic performance of dye-sensitized nanocrystalline TiO2 solar cells

The effect mechanism of triphenyl phosphate (TPP) is studied as an effective and inexpensive additive in the electrolyte of dye-sensitized solar cells (DSSCs) performance. The N719- and TPA-sensitized devices with a modified electrolyte show high efficiencies of 7.04% and 2.73% under 100 mW cm(-2) light illumination, respectively. The enhancement in V-oc arises from increasing electron density in the conduction band (CB) of TiO2 that leads to a shift in the Fermi level (E-F) and thereby a suppression in electron recombination occurs. Electrochemical and spectroscopic data exhibit slower electron recombination and indicates that TPP forms a charge transfer complex with iodine in the electrolyte. This complexation decreases the concentration of free triiodide and limits the electron recombination so that it improves J(sc). Furthermore, the results reveal that TPP is a suitable inexpensive alternative for 4-tert-butylpyridine (TBP) additive in the DSSCs. We replaced TBP with TPP in DSSC based on TPA dye and observed an 73% increase in eta compared to the blank electrolyte (without additive). Also, we investigate the effects of substituents in the phosphate additive structure on the photovoltaic properties by comparing our findings with previous work and found that the aliphatic phosphate additives exhibit a better performance compared to aromatic phosphate additives in the DSSCs.