Enhancing DSSCs and Photocatalytic Hydrogen Production with D-A-A-π-A Sensitizers Containing 10'H-Spiro [Fluorene-9,9'-Phenanthren]-10'-one and Benzo[c][1,2,5]Thiadiazole.

Novel D-A-A-π-A organic sensitizers (FZ-sensitizer), utilizing spiro [fluorene-9,9'-phenanthren]-10'-one and benzo [c][1,2,5]thiadiazole moiety as two auxiliary acceptors, are synthesized and applied in dye-sensitized solar cells (DSSCs) and hydrogen production. By incorporating a bulky spiro [fluorene-9,9'-phenanthrene]-10'-one (A) and benzo[c][1,2,5]thiadiazole (A) between the donor (D) and π-bridge moiety, structural modifications inhibit molecular aggregation, while the carbonyl group enhances the capture of Li ions, thereby delaying charge recombination. Furthermore, the extended π-conjugation broadens the light absorption range and enhances the power conversion efficiency (PCE) of FZ-2 under AM1.5 conditions, achieving up to 5.72%. Co-sensitization with N719 and FZ-2 shows PCE of 9.60% under one sun. Under TL84 indoor light conditions, the efficiency is 29.69% at 2500 lux. The superior co-sensitization performance of N719 and FZ-2 can be attributed to FZ-2's high absorptivity at short wavelengths, compensating for N719's shortcomings in this range. FZ-sensitizers also exhibit high efficiency in photocatalytic hydrogen production. The hydrogen production activities of FZ-2 are 9190 μmol/g (1 hour) and 76582 μmol/g (12 hours) respectively, while those of FZ-1 are 7430 μmol/g (1 hour) and 64004 μmol/g (12 hours), indicating that FZ-2 can inject charges into TiO more efficiently and utilize them for water splitting. Stability testing of photocatalytic water splitting after 12 hours shows a turnover number (TON) of 4249 for FZ-1 and 5378 for FZ-2.