Dye-sensitized solar cells based on a donor-acceptor system with a pyridine cation as an electron-withdrawing anchoring group.

New hemicyanine dyes (CM101, CM102, CM103, and CM104) in which tetrahydroquinoline derivatives are used as electron donors and N-(carboxymethyl)-pyridinium is used as an electron acceptor and anchoring group were designed and synthesized for dye-sensitized solar cells (DSSCs). Compared with corresponding dyes that have cyanoacetic acid as the acceptor, N-(carboxymethyl)-pyridinium has a stronger electron-withdrawing ability, which causes the absorption maximum of dyes to be redshifted. The photovoltaic performance of the DSSCs based on dyes CM101-CM104 markedly depends on the molecular structures of the dyes in terms of the n-hexyl chains and methoxyl. The device sensitized by dye CM104 achieved the best conversion efficiency of 7.0% (J(sc) = 13.4 mA cm(-2), V(oc) = 704 mV, FF = 74.8%) under AM 1.5 irradiation (100 mW cm(-2)). In contrast, the device sensitized by reference dye CMR104 with the same donor but the cyanoacetic acid as the acceptor gave an efficiency of 3.4% (J(sc) =6.2 mA cm(-2), V(oc) = 730 mV, FF = 74.8%). Under the same conditions, the cell fabricated with N719 sensitized porous TiO(2) exhibited an efficiency of 7.9% (J(sc) = 15.4 mA cm(-2) , V(oc) = 723 mV, FF = 72.3%). The dyes CM101-CM104 show a broader spectral response compared with the reference dyes CMR101-CMR104 and have high IPCE exceeding 90% from 450 to 580 nm. Considering the reflection of sunlight, the photoelectric conversion efficiency could be almost 100% during this region.