Synthesis, Photophysics, and Photovoltaic Studies of Ruthenium Cyclometalated Complexes as Sensitizers for p-Type NiO Dye-Sensitized Solar Cells

Abstract

We report the first application of cyclometalated ruthenium complexes of the type Ru[(N∧N)2(C∧N)]+ as sensitizers for p-type NiO dye-sensitized solar cells (NiO p-DSCs). These dyes exhibit broad absorption in the visible region. The carboxylic anchoring group is attached to the phenylpyridine ligand, which results in efficient hole injection. Moreover, the distance between the Ru[(N∧N)2(C∧N)]+ core and the carboxylic anchoring group is systematically varied by inserting rigid phenylene linkers. Femtosecond transient absorption (TA) studies reveal that the interfacial charge recombination rate between reduced sensitizers and holes in the valence band of NiO decreases as the number of phenylene linkers increases across the series. As a result, the solar cell made of the dye with the longest spacer (O12) exhibits the highest efficiency with both increased short-circuit current (Jsc) and open-circuit voltage (Voc). The incident photon-to-current conversion efficiency (IPCE) spectra match well with the absorpt...