Narrowing band gap of platinum acetylide dye-sensitized solar cell sensitizers with thiophene π-bridges

A new family of linear structure Pt(II) (triphenylamine alkynyl) 2(triethyl-phosphine) (2-carboxy-2-cyanovinyl-X-alkynyl) (where X thiophene (PT1), [2, 2']-bi-thiophene (PT2) or 1,2-di(2-thienyl) ethylene) (PT3)) complexes have been synthesized and characterized. The introduction of thiophene pi-bridges enhanced the extent of electron delocalization over the whole molecules, so their maximum absorption peaks were red shifted. These complexes have been tested as dye-sensitized solar cell (DSSC) sensitizers. PT2 showed the best photovoltaic performance, yielding 4.21% power conversion efficiency using a volatile electrolyte. As shown in an electrochemical impedance experiment, the different charge transfer resistance (R-ct) of the three sensitizers influences their injection lifetime of electrons and then their photoelectrical properties.