Effect of coadsorbents on DSSC sensitized by NIR absorbing poly(ethyl thieno[3,4-b]thiophene-2-carboxylate)

Poly(ethyl thieno[3,4-b]thiophene-2-carboxylate) (PTTEt), showing near infrared (NIR) absorption was employed as a polymer sensitizer in dye-sensitized solar cell (DSSC). The photovoltaic performance of DSSC was investigated with PTTEt of different molecular weights. Low molecular weight aliphatic di-acids were also employed as coadsorbents along with PTTEt. It was revealed that the reduction of polymer molecular weights caused only a slight enhancement in overall power conversion efficiency (η). The species and concentration of coadsorbents, on the other hand, greatly affects η. The best performance with η of ca. 1.5% was obtained when 3,3′-dithiodipropionic acid was adsorbed along with PTTEt, indicative of significant improvement of η (ca. 50% increase).