Novel heteroleptic ruthenium(II) complex with a terpyridine derivative for dye-sensitized solar cells

In this work, we designed and investigated theoretically a novel heteroleptic ruthenium(II) complex [Ru(dcbpy)(dtbpy)(NCS)2] (dcbpy: 4,4′-dicarboxy-2,2′-bipyridine, dtbpy: 4,4′-di terpyridine-2,2′-bipyridine) with a terpyridine derivative to increase the absorption ability as compared to the N3 dye([Ru(dcbpy)2)(NCS)2]). Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations were used to gain insight into the factors responsible for the photovoltaic properties of dye sensitizers. The absorption spectrum of the dye with the terpyridine derivative showed higher molar extinction coefficients and broader bands than those that the spectra of the dyes without the terpyridine derivative, especially in the region between 400 nm and 650 nm. This is attributed to the electron-donating characteristic of the terpyridine moiety. According to the molecular orbital analysis, we observed that the LUMO+1 and the LUMO+3 were mainly localized on the terpyridine moiety. The HOMO → LUMO+1 and LUMO+3 transitions dominated in the region between 400 nm and 650 nm, showing the key role of the terpyridine moiety in that region. In terms of the panchromatic feature, the [Ru(dcbpy)(dtbpy)(NCS)2] is expected to have a better performance in short-circuit photocurrent (Jsc) than the [Ru(dcbpy)2)(NCS)2].