Molecular engineering of D-D-π A type organic dyes incorporating indoloquinoxaline and phenothiazine for highly efficient dye sensitized solar cells

Four metal-free organic dyes QX05-08 based on indoloquinoxaline and phenothiazine have been successfully designed and synthesized for dye-sensitized solar cells. The D-D-pi-A type dyes QX07 and QX08 consist of an indoloquinoxaline donor, a phenothiazine donor, a cyanoacrylic acid acceptor/anchoring group and a thiophene or furan pi-bridge. Other simple D-pi-A type dyes QX05 and QX06 based on indoloquinoxaline and phenothiazine respectively have also been synthesized for comparison. The D-D-pi-A type dyes QX07 and QX08 present good balanced structures and show excellent photoelectric properties. Especially, the dye QX07 with a thiophene unit as the pi-bridge exhibits the best photovoltaic performances in solar cells. A high power conversion efficiency up to 8.28% with a J(sc) of 15.3 mA cm(-2) and a V-oc of 757 mV have been achieved by the dye 0)107 using an iodine electrolyte under standard conditions. (C) 2016 Elsevier B.V. All rights reserved.