Incorporation of Thienylenevinylene and Triphenylamine Moieties into Polythiophene Side Chains for All-Polymer Photovoltaic Applications

We report all-polymer photovoltaic cells using poly(1,4-dioctyloxyl-p-2,5-dicyanophenylenevinylene) (DOCN-PPV) as electron acceptor and a series of polythiophene (PT) derivatives P1 to P3 as electron donors. Among the polymer donors, P2 and P3 are new PT derivatives with functionalized and conjugated tri(thienylenevinylene) (TTV) and triphenylaminevinylene (TPAV) side chains, and they are characterized by absorption spectroscopy, cyclic voltammetry, and hole mobility, as well as morphology measurements. Photovoltaic results indicate that the device performance is sensitive to the presence of functionalized side chains within the molecular structure. To be specific, P1, without the functionalized side chains, yields the lowest power conversion efficiency (PCE) while P3, with both the TTV and TPAV side chains, shows a 2-fold increase in efficiency over P2 with only the TTV side chain, reaching a PCE of 0.44% under simulated AM 1.5 illumination at 100 mW/cm(2). We attribute the enhancement of PCE to the improved absorption and enhanced hole mobility, as well as a better morphological structure of P3.