Novel indeno[1,2-b]indole-spirofluorene donor block for efficient sensitizers in dye-sensitized solar cells

Abstract

Indeno[1,2-b]indole-spirofluorene (IISF) unit has been synthesized and firstly applied as a donor candidate for the sensitizer of dye-sensitized solar cells. Two new dyes JY57 and JY58, based on IISF donor, are consequently constructed, together with dithieno[3,2-b:2′,3′-d]pyrrole (DTP) as π-bridge and cyanoacrylic acid as acceptor. For JY58, additional electron-withdrawing 2,1,3-benzothiadiazole unit is inserted between IISF donor and DTP π-bridge to achieve a broader absorption range. Both dyes show high JSC and good device performance in iodine electrolyte. The photovoltaic properties are further tuned by co-adsorption and co-sensitization strategies, and better PCEs are obtained. Among the series of cells under AM 1.5G irradiation, cells fabricated by the synergic adsorption of JY57, chenodeoxycholic acid and JY59, achieve the highest PCE of 9.56%, which is much higher than 8.46% for N719 at the same condition.