Tuning the Absorption, Charge Transport Properties, and Solar Cell Efficiency with the Number of Thienyl Rings in Platinum-Containing Poly(aryleneethynylene)s

The synthesis, characterization, and photophysics of a series of solution-processable and strongly
visible-light absorbing platinum(II) polyynes containing bithiazole-oligo(thienyl) rings were presented. Tuning
the polymer solar cell efficiency, as well as optical and charge transport properties, in soluble, low-band
gap PtII-based conjugated poly(heteroaryleneethynylene)s using the number of oligothienyl rings is described.
These materials are highly soluble in polar organic solvents due to the presence of solubilizing bithiazole
moieties and show strong absorptions in the solar spectra, rendering them excellent candidates for bulk
heterojunction polymer solar cells. Their photovoltaic responses and power conversion efficiencies (PCEs)
depend to a large extent on the number of thienyl rings along the main chain, and some of them can be
used to fabricate highly efficient solar cells with PCEs of up to 2.7% and a peak external quantum efficiency
to 83% under AM1.5 simulated solar illumination, which is comparable to that of poly(3-hexylthiophene)-based devices fabricated without additional processing (annealing or TiOx layer). The influence of the number
of thienyl rings and the metal group on the performance parameters and optimization of solar cell efficiency
was evaluated and discussed in detail. At the same blend ratio of 1:4, the light-harvesting ability and PCE
increase sharply as the thienyl chain length increases. The present work provides an attractive approach
to developing conjugated metallopolymers offering broad solar absorptions and tunable solar cell efficiency
and demonstrates the potential of metalated conjugated polymers for efficient power generation.