Refining the anchor: optimizing the performance of cyclometallated ruthenium(II) dyes in p-type dye sensitized solar cells

A comparison of the performances of p-type dye sensitized solar cells (DSCs) sensitized by three cyclometallated ruthenium(II) dyes differing in their anchoring domains is presented. The dyes are [Ru(bpy) 2 (H 1 )] (H 3 1 = (4-(2-phenylpyridin-4-yl)phenyl)phosphonic acid) and the salts [ n Bu 4 N][Ru(bpy) 2 ( 1 )] and [Ru(bpy) 2 (H 2 )][PF 6 ] (H 2 2 = (4-(2-phenylpyridin-4-yl)phenyl)carboxylic acid). DSCs were fabricated with FTO/NiO working electrodes and either an I 2 /I 3 – /MeCN or I 2 /I 3 – /MeCN:EtCN (3:1 by volume) electrolyte. The results confirm the higher performance of dyes with a phosphonate versus carboxylic acid anchor, and reveal that [Ru(bpy) 2 (H 1 )] ( J SC = 3.24 mA cm –2 and η = 0.116%) performs better than [Ru(bpy) 2 ( 1 )] – . Electrochemical impedance spectroscopy (EIS) shows that a DSC with [Ru(bpy) 2 (H 1 )] offers the lowest transport and recombination resistances and the shortest hole lifetime and diffusion length