Organic sensitizers with a rigid dithienobenzotriazole-based spacer for high-performance dye-sensitized solar cells

New D-π-A type sensitizers ( YC dyes), comprising arylamine as the electron donor, dithieno[3′,2′:3,4;2′′,3′′:5,6]benzo[1,2- d ][1,2,3]triazole ( DTBZ ) as the rigidified π-conjugated spacer, and 2-cyanoacrylic acid as both the acceptor and anchor, have been synthesized. The YC sensitizers displayed broad absorption of light, from 362 nm to 550 nm, with a molar extinction coefficient as high as ∼54 800 M −1 cm −1 . The light-to-electricity conversion efficiencies of the dye-sensitized solar cells (DSSCs) ranged from 5.82 to 8.51% under simulated AM 1.5 G illumination. Upon addition of 5 mM of CDCA as a coadsorbent, the best performing cell displayed an efficiency of 9.10%, surpassing that of the N719 -based standard cell (8.12%), and even achieved an efficiency of 10.56% under quarter sunlight illumination. Sensitizers with a rigidified spacer show J-aggregation enhanced photon-to-electron conversion of DSSCs and cell efficiencies up to 9.1% (1 sun) and 10.6% (0.25 sun), respectively.