A new alternating copolymer of dithienosilole and thienopyrrole-4,6-dione (PDTSTPD) possesses both a low optical bandgap (1.73 eV) and a deep highest occupied molecular orbital energy level (5.57 eV). The introduction of branched alkyl chains to the dithienosilole unit was found to be critical for the improvement of the polymer solubility. When blended with PC(71)BM, PDTSTPD exhibited a power conversion efficiency of 7.3% on the photovoltaic devices with an active area of 1 cm(2).

Direct (hetero)arylation polymerization (DHAP) has recently been established as an environmentally benign method for the preparation of conjugated polymers. This synthetic tool features the formation of C-C bonds between halogenated (hetero)arenes and simple (hetero)arenes with active C-H bonds, thereby circumventing the preparation of organometallic derivatives and decreasing the overall production cost of conjugated polymers. Since its inception, selectivity and reactivity of DHAP procedures have been improved tremendously through the careful scrutinity of polymerization outcomes and the fine-tuning of reaction conditions. A broad range of monomers, from simple arenes to complex functionalized heteroarenes, can now be readily polymerized. The successful application of DHAP now leads to nearly defect-free conjugated polymers possessing comparable, if not slightly better, characteristics than their counterparts prepared using classical cross-coupling methods. This comprehensive review describes the mechanisms involved in this process from experimental and theoretical standpoints, presents an up-to-date compendium of materials obtained by this means, and exposes its current limitations and challenges.

A series of low‐bandgap alternating copolymers of dithienosilole and thienopyrrolodione (PDTSTPDs) are prepared to investigate the effects of the polymer molecular weight and the alkyl chain length of the thienopyrrole‐4,6‐dione (TPD) unit on the photovoltaic performance. High‐molecular‐weight PDTSTPD leads to a higher hole mobility, lower device series resistance, a larger fill factor, and a higher photocurrent in PDTSTPD:[6,6]‐phenyl C71 butyric acid methyl ester (PC71BM) bulk‐heterojunction solar cells. Different side‐chain lengths show a significant impact on the interchain packing between polymers and affect the blend film morphology due to different solubilities. A high power conversion efficiency of 7.5% is achieved for a solar cell with a 1.0 cm2 active area, along with a maximum external quantum efficiency (EQE) of 63% in the red region.

Don't stand Stille: A direct heteroarylation polycondensation reaction was used for the synthesis of high‐molecular‐weight thienopyrroledione‐based polymers (see scheme) in an impressive yield (up to 96 %) and in only a few synthetic steps. This new method is an alternative to the standard Stille coupling reaction and thus avoids formation of toxic tin by‐products.

A new class of low-bandgap copolymers based on benzodithiophene (BDT) and thieno[3,4-c]pyrrole-4,6-dione (TPD) units is reported. Chemical modifi cations of the conjugated backbone promote both high molecular weights and processability while allowing for tuning of the electronic properties. Copolymers with substituted thiophene spacers (alkyl chains facing the BDT unit) or unsubstituted thiophene spacers tend to have low power conversion effi ciencies (PCE less than 1%) due to a bad morphology of the active layer, whereas copolymers with substituted thiophene spacers (alkyl chains facing TPD unit) show enhanced morphology and PCEs up to of 3.9%. Finally, BDT-TPD copolymers without any thiophene spacers still show the best performances with power conversion effi ciencies up to 5.2%.

Many diketopyrrolopyrrole-based (DPP) polymers have shown remarkable transport properties and to fabricate cost efficient materials, the new direct (hetero)arylation polymerization (DHAP) could become a valuable tool.

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An efficient route for the synthesis of 1-iodo-5-octyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione as a key intermediate to build new electron-deficient monomers and related conjugated polymers is reported. Along these lines, two new low bandgap copolymers were synthesized from Stille or Suzuki coupling. These polymers were characterized and their properties compared to those of analogous conjugated polymers.