Quinoline‐Coupled Coumarin‐Based Ruthenium(II) Dye Sensitizer for Photoelectrochemical Cells and Solar Cells: A Mimic for an Artificial‐Light‐Harvesting System

The conversion of solar energy into chemical energy by the use of dye‐sensitized solar cells (DSSCs) and dye‐sensitized photoelectrochemical cells (DSPECs) has been considered a convenient method in recent years. Herein, DSPEC and DSSC devices are fabricated by mimicking the function of photosystem II in natural photosynthesis with a new quinoline‐coupled coumarin‐based ruthenium(II) dye (RQC)‐sensitized TiO 2 semiconductor as the light‐harvesting center. By using the RQC‐sensitized TiO 2 as the working electrode, photoelectrochemical water‐splitting reactions are effectively conducted in a phosphate buffer solution (pH = 6), with 30 m m triethanolamine as the sacrificial electron donor. Oxygen and hydrogen bubbles are evolved from the working electrode and counter electrode, respectively. By applying +0.78 V potential versus a relative hydrogen electrode, an initial photocurrent density of 11.07 mA cm −2 and a final photocurrent density of 9.66 mA cm −2 are achieved. Under this condition, a maximum photoelectrochemical water splitting efficiency of 4.98% is obtained. The photocurrent–voltage ( J – V ) characterization of the DSSC device fabricated with RQC under standard AM 1.5G illumination furnishes a J sc of 11.4 mA cm −2 , V oc of 0.69 V, fill factor of 0.53, and power conversion efficiency ( η ) of 4.16%.