Abstract
In this study we explore the substituent effects of a class of Ru(ii)-based sensitizers bearing a 4,4′,4′′-tricarboxy-2,2′:6′,2′′-terpyridine anchor, a functional pyridinyl azolate and a single thiocyanate ligand. Three sensitizers, i.e.PRT-tBu, ND-1 and ND-2, with t-butyl, 5-[4-[bis(4-hexyloxyphenyl)amino]phenyl]-2-thienyl and 5-[7-[4-[bis(4-hexyloxyphenyl)amino]phenyl]-4-(2,1,3-benzothiadiazolyl)]-2-thienyl substituents are designed and synthesized. Their photophysical and redox properties are probed using UV/vis absorption and cyclic voltammetry studies. The DSC cell performances (J SC , V OC and PCE) were also examined and analyzed in order to elucidate the structure-property relationships. It is notable that all sensitizers showed superior spectral responses in the region up to 830 nm, among which the PRT-tBu and ND-1 showed prolonged electron lifetimes, suppressed electron recombination and higher power conversion efficiencies (PCE) compared to the third sensitizer PRT-ND2 with a benzothiadiazolyl linker at the ancillary chelate. In particular, the optimized DSC device using the PRT-tBu sensitizer gives a J SC of 16.29 mA cm -2 , a V OC of 787 mV and a fill factor (FF) of 0.75, corresponding to an overall PCE of 9.68% under standard global AM 1.5 solar irradiation. Its adequate performance plus simplified synthetic procedures warrant its application in larger sized DSCs.