Ethynylene-linked planar rigid organic dyes based on indeno[1,2-b]indole for efficient dye-sensitized solar cells

Three metal-free push pull type organic dyes QX19-21 based on indeno[1,2-b]indole donor have been synthesized for dye-sensitized solar cells (DSSCs). In order to obtain good cell performance, an ethynylene linker was inserted into the dye skeleton to extend pi-conjugated planar rigid structure and three hexyl groups were involved to prevent dye aggregation. The dyes QX19 and QX20 employing phenylene and thiophene as the pi-bridges were designed as a D-pi-A structure. As for the dye QX21, a benzothiadiazole was inserted as the secondary acceptor to construct as a D-A-pi-A structure. All three dyes based cells exhibited high photovoltages and good DSSC performances. A high PCE of 7.99% was obtained by the dye QX21 under AM 1.5G irradiation. Especially, the co-sensitization of QX21 with QX20 achieved the further improved PCE up to 8.37%. (C) 2017 Elsevier Ltd. All rights reserved.