π- Extended Dinuclear Ruthenium(II) Complex for Dye-Sensitized Solar Cell

Dye-sensitized solar cells (DSSCs) have beenevaluated for photovoltaic applications because of theirlow cost and high-power conversion efficiency [۱].Polypyridyl ruthenium complexes with ligandsfunctionalized by thiophene, carbazole, and and π-extended moiety can be regarded as super sensitizers [۱].Herein, a new π-extended binuclear ruthenium (II)complex (BiRu۲) with two naphthyl moiety wasdesigned and synthesized and used as dye in DSSC. CVresults showed that the E۱/۲ oxidation of BiRu۲ dye isshifted negatively by ۰.۰۲ V compared to the N۳ couple,as standard dye, [۲] indicating stronger electron-donatingability of the fused π-expanded ligand than H۲dcbpy. The calculated excited state oxidationpotential (E* = -۰.۹۷ V) for BiRu dye is close to N۳ dye and sufficiently more negative than theconduction band (CB) edge level of the TiO۲ at approximately -۰.۷ V [۱, ۳] indicating energicallyhighly favorable for electron injection from the excited dyes into the conduction band of TiO۲.Moreover, the estimated LUMO energy of BiRu۲ dye (-۳.۳ eV) is higher than the conduction bandenergy level of the TiO۲ (-۴.۰ eV) which is desirable for more efficient electron injection into CBof TiO۲ [۴]. The DSSC based on BiRu۲ achieves a conversion efficiency of ۵.۲۱%, which is ۱۲%higher than that of the N۳-sensitized solar cell under the same cell fabrication and efficiencymeasuring procedures (See I-V curve), which is attributed to the higher absorption coefficient inthe visible region of specrum and lower E۱/۲ of BiRu۲ as a result of π-expanded ligand. Moreover,the improved JSC and VOC were caused by the avoided aggregation of BiRu۲ dye, because of itsbulky structure which could decrease the recombination and intermolecular charge transfer [۳]. Inconclusion, we prepared a new sensitizer, BiRu۲, by incorporating naphthyl antennas into theancillary ligands and investigated its potential as dye in DSSC device which shows the betterperformance respect to the N۳. The improvement performance of DSSC device based on BiRu۲reveal the great potential of this dye for DSSC application in the future.

کلیدواژه ها:

π-Extended ligand ، Dinuclear ruthenium (II) sensitizer ، Dye sensitized solar cell