Novel Ruthenium Sensitizers Designing for Efficient Light Harvesting under Both Sunlight and Ambient Dim Light

The dye-sensitized solar cell (DSC) is a proven technology that operates efficiently under both sunlight and ambient dim light. However, because sunlight is significantly different from ambient dim light in terms of irradiance and emission spectrum, designing a single sensitizer that can perform equally efficiently under both conditions remains practically difficult. For the first time, panchromatic Ru(II) sensitizers bearing the tBu substituted 6-quinolin-8-yl-2,2'-bipyridine anchor and 2,6-bis(pyrazolyl)pyridine ancillary with peripheral CF₃ and C₃F₇ substituents and central tBu substituent are synthesized to provide superior conversion efficiency. The quinolin-8-yl-2,2'-bipyridine anchor enhances the spectrum response from 550 to 700 nm, which is particularly important to fluorescent light spectrum. Furthermore, the introduction of bulky C₃F₇ and tBu groups effectively increase the steric hindrance that allows better dye uptake and suppresses interfacial recombination, both of which are important for light harvesting under dim light. The champion device in this study exhibits a remarkable power conversion efficiency of 31.82% under 6000 lux fluorescent light without the use of a cosensitizer. Meanwhile, the device also shows a high PCE of 10.37% under simulated 1 sun irradiation, making it the first ruthenium sensitizer suitable for both high and dim light applications under the same fabrication condition in DSC.