Direct Arylation Polycondensation (DAP) Synthesis of Alternating Quaterthiophene-Benzothiadiazole Copolymers for Organic Solar Cell Applications

Tina Keller, Tobias Gahlmann, Thomas Riedl, Ullrich Scherf

Chempluschem. 2019 Sep;84(9):1249-1252.

PMID: 31944056

Abstract:

Poly[(2,1,3-benzothiadiazole-4,7-diyl)-alt-4',3''-difluoro-3,3'''-di(2-octyldodecyl)-2,2';5',2'';5'',2'''-quaterthiophene-5,5'''-diyl)] (PBTff4T-2OD) and poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-3,3'''-di(2-octyldodecyl)-2,2';5',2'';5'',2'''-quaterthiophene-5,5'''-diyl)] (PffBT4T-2OD) for use as the p-donor component of high-efficiency fullerene-based organic solar cells are usually synthesized in established C-C cross-coupling reactions, preferably using the Stille procedure. This report describes how PBTff4T-2OD and PffBT4T-2OD are generated in a direct arylation polycondensation (DAP) approach with molecular weights up to Mn =19.4 kDa and 21.1 kDa, respectively, and how structural defects in the copolymers (e. g., homocoupling defects) show a strong impact on the pre-aggregation behavior. The optimized reaction conditions allow for a distinct reduction of the amount of such defects in the resulting copolymers. When the Stille-type products are used in the active layer of organic solar cells (OCSs) together with fullerene acceptors, high power-conversion efficiencies (PCEs) in the range of 8.6-10.8 % have been reported. The high PCEs are particularly related to the pre-aggregation of the conjugated copolymers prior to film formation. Despite quite similar characterization data, non-optimized OCSs with the DAP polymers as replacement for the Stille products afforded a relatively low power-conversion efficiency of up to 2.4 %.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP132814916	3,3′′′-Dihexyl-2,2′:5′,2′′:5′′,2′′′-quaterthiophene		132814-91-6	Price
AP5632291	2,2′:5′,2′′:5′′,2′′′-Quaterthiophene		5632-29-1	Price

Catalog Number

Product Name

Structure

CAS Number

Price

AP132814916

3,3′′′-Dihexyl-2,2′:5′,2′′:5′′,2′′′-quaterthiophene

132814-91-6

Price

AP5632291

2,2′:5′,2′′:5′′,2′′′-Quaterthiophene

5632-29-1

Price

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