A facile and convenient synthesis and photovoltaic characterization of novel thieno[2,3-b]indole dyes for dye-sensitized solar cells

Abstract

Two novel dyes IK-1,2 bearing the 8-alkyl-8H-thieno[2,3-b]indole unit as an electron-donating part of the push–pull system have been designed and prepared, as promising sensitizers for solar cells. The key steps of the synthesis involve the crotonic condensation of 1-alkylisatins with 2-acetylthiophene, followed by reduction of the CC double bond and further cyclization through the Paal–Knorr reaction with the Lawesson reagent, thus leading to the formation of 2-(thien-2-yl) substituted thieno[2,3-b]indole derivatives. The optical and electrochemical properties of these dyes have been investigated by using spectrophotometry and cyclic voltammetry respectively, while their photovoltaic performance was evaluated by a device fabrication study. The DSSCs based on IK-1 and IK-2 have demonstrated an efficiency of η=0.37% (FF=73%) and η=0.79% (FF=69%) under 100mWcm−2 simulated AM 1.5G solar irradiation, respectively.