A thiazolothiazole�thiophene semiconducting polymers, PTzBT-14HD, originally developed for organic field-effect transistors, are examined as the p-type material for bulk heterojunction solar cells with PC61BM.  It is found that the increase of molecular weight on PTzBT-14HD leads to high efficiencies of 5.7% with the optimal Mn of 33 kDa.  Structural studies of the polymer thin films reveals that, in fact, the increase of molecular weight brings about high orientational order of the polymer domains in the thin film and, interestingly, drastic changes in the orientation when blended with PC61BM.  While in the polymer-only thin film, the polymer tends to orient in an edge-on manner, in the presence of PC61BM, the polymer shows a strong tendency to form a face-on orientation with the increase of molecular weight, which critically rationalizes the high efficiencies in the high-molecular weight polymers.

Drastic change of molecular orientation in thiazolothiazole copolymers by molecular weight control and blending with PC<sub>61</sub>BM leads to high efficiencies in solar cells

243rd National Meeting (2012)

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Drastic change of molecular orientation in thiazolothiazole copolymers by molecular weight control and blending with PC61BM leads to high efficiencies in solar cells

Drastic change of molecular orientation in thiazolothiazole copolymers by molecular weight control and blending with PC₆₁BM leads to high efficiencies in solar cells