Auxiliary Triazatruxene Donor‐Based Squaraine Dyes for Dye‐Sensitized Solar Cells: <i>Cis‐</i> and <i>Trans‐</i> Configuration of Dyes for Modulating Photophysical and Electronic Properties

In DSSCs, dye regeneration efficiency and dye aggregation on the TiO₂ surface can be modulated by using bulky aromatic donors wrapped with alkyl groups. Introduction of rigid aromatic rings around the donor unit of a dye will directly impact the driving force for electron injection and dye regeneration of a dye. In this work, we designed and synthesized KNS dyes with an auxiliary TAT donor integrated with a visible active squaraine dye. Here, octupolar-structured auxiliary TAT wrapped with alkyl groups is used as a strong donor and shelter to reduce the dye aggregation and charge recombination process. Further, to improve the light-harvesting efficiency and incident photon-to-current conversion efficiency of DSSC devices fabricated with KNS dyes, the central squaric acid unit has been modified by appending the electron-withdrawing dicyano group at the central squaric unit, and the trans-configured KNS1 dye was converted to cis-configured KNS2 dye. The power conversion efficiency of devices based on the KNS dyes was studied with and without 3 equivalents of CDCA by using the I^-/I₃ ^- electrolyte. Out of these devices, the KNS1: CDCA (1:3) based cell exhibited the best PCE of 6.25% with V_OC of 793 mV, J_SC of 11.08 mA cm^-2, and ff of 71%.