New low-bandgap polymetallaynes of platinum functionalized with a triphenylamine-benzothiadiazole donor-acceptor unit for solar cell applications

Two new solution-processable platinum-containing polymetallayne polymers functionalized with both triphenylamine and 2,1,3-benzothiadiazole groups were synthesized and characterized by thermal, spectroscopic and electrochemical methods. Their corresponding diplatinum model complexes were also prepared for comparison. The organometallic polymers exhibit good thermal stability and intense low-energy absorption bands in the visible region and both of them are fluorescent red-emitting materials. The effect of thiophene addition along the polymer chain on the optical, luminescent and photovoltaic properties of these metallated materials was also examined. Bulk heterojunction solar cells based on these polymers were studied and the low-bandgap polymers with internal donor-acceptor-donor π-conjugated fragment can serve as a good electron donor for fabricating photovoltaic devices by blending the polymer with a methanofullerene electron acceptor. At the same donor:acceptor blend ratio of 1:4, the light-harvesting ability and solar cell efficiency notably increase with the incorporation of additional thiophene rings in the polymer. The best power conversion efficiency of 1.61% was achieved with the open-circuit voltage of 0.77 V, short-circuit current density of 4.94 mA cm^-2 and fill factor of 0.39 under illumination of an AM 1.5 solar cell simulator.