Fine tuning of the photovoltaic properties of triarylethylene-bridged dyes by altering the position and proportion of phenyl/thienyl groups

Four triarylethylene (TAE) pi-spacers have been applied for Y-shaped dyes in dye-sensitized solar cells (DSSCs) and their effects on photovoltaic performance have been fully investigated. All photosensitizers inherit the ability of three-dimensional TAE to weaken the pi-pi stacking in aggregation state, while their suppression on charge recombination in electrolytes presents a high reliance on the position and proportion of phenyl/thienyl groups embedded in TAE moieties. In iodine electrolytes, benzene-rich triphenylethene-based dye JY65 achieves the best open-circuit voltage of 739 mV, sharply higher than that of 614 mV for trithienylethene (TTE)-based dye JY63. Moreover, dyes JY64 and D-1 with hetero-TAE-bridge tend to show better power convention efficiency (PCE) stemming from the higher short-circuit current density and moderate open-circuit voltage. Whereas in cobalt electrolytes, the TTE-bridged JY63 attains a superior PCE of 5.84%, inversely surpassing the value of 5.28% based on D-1 under the same condition. Therefore, tuning the TAE skeletons via altering the position and proportion of aryl groups in it would bring in a promising design for anti-stacking sensitizers to meet the varied demand in DSSCs.