Connecting Direct C-H Arylation Reactions with Dye-Sensitized Solar Cells: A Shortcut to D-A-π-A Organic Dyes

A step-economical synthetic strategy is developed to target thieno[3,4-c]pyrrole-4,6-dione (TPD)-based D-A-π-A organic dyes for dye-sensitized solar cells (DSSCs). Through sequential Pd-catalyzed direct C-H (hetero)arylation reaction, synthesis of the push-pull-type small molecules is reduced from the traditional six steps to two steps. In this report, we focus on the optimization of the key C-H monoarylation of TPD by screening ligands, acid additives, bases, and solvents. The reaction proves versatile toward new D-A-π-A organic dyes with a variety of different donor groups, and several derivatives are efficiently prepared under optimum reaction conditions. The sensitive aldehyde functionality that is a required intermediate for conversion into anchoring groups for TiO₂ is well tolerated. Based on our synthetic study, DSSCs are fabricated and characterized using two designed sensitizers. The photovoltaic characterization of the devices affords an open-circuit voltage of 0.60-0.69 V, a short-circuit current density of 10.85-11.07 mAcm^-2, and a fill factor of 69.9-70.8%, which corresponds to an overall power conversion efficiency of 4.61-5.33%.