Low-Band-Gap Platinum Acetylide Polymers as Active Materials for Organic Solar Cells

We report on two pairs of platinum acetylide based polymers and model oligomers utilizing a 2,1,3-benzothiadiazole (BTD) acceptor moiety flanked on either side by either 2,5-thienyl donor units (Pt2BTD-Th and p-PtBTD-Th) or (3,4-ethylenedioxy)-2,5-thienyl donors (Pt2BTD-EDOT and p-PtBTD-EDOT). Both oligomer/polymer pairs absorb strongly throughout the visible region; however, because the (ethylenedioxy)thiophene moiety is a stronger donor than thiophene, the latter oligomer/polymer pair has a correspondingly lower band gap and, therefore, harvests light more efficiently at longer wavelengths. p-PtBTD-Th exhibits a relatively narrow molecular weight distribution with a number-average molecular weight (Mn) of 22 kDa, while p-PtBTD-EDOT exhibits a comparable Mn of 33 kDa but has a high polydispersity index likely due to aggregation. We provide a complete report of the photophysical and electrochemical characterization of the two oligomer/polymer pairs. The photophysical studies reveal that the materials unde...