Direct Arylation Strategies in the Synthesis of π-Extended Monomers for Organic Polymeric Solar Cells

Abstract

π-conjugated macromolecules for organic polymeric solar cells can be rationally engineered at the molecular level in order to tune the optical, electrochemical and solid-state morphology characteristics, and thus to address requirements for the efficient solid state device implementation. The synthetic accessibility of monomers and polymers required for the device is getting increasing attention. Direct arylation reactions for the production of the π-extended scaffolds are gaining importance, bearing clear advantages over traditional carbon-carbon forming methodologies. Although their use in the final polymerization step is already established, there is a need for improving synthetic accessibility to implement them also in the monomer synthesis. In this review, we discuss recent examples highlighting this useful strategy.

Donor–acceptor conjugated copolymers incorporating tetrafluorobenzene as the π‐electron deficient unit

“…The polymers have however interesting HOMO–LUMO gaps. In the light of the possibility to use oligomer molecules for photovoltaics, which overcome shortcomings of both vapor‐deposited small molecules and solution processed polymers, these structures can represent, once thorough optimization of the polymerization methodology has been successfully carried out, promising alternatives for state‐of‐the‐art organic photovoltaics …”

Molecular weight tuning of low bandgap polymers by continuous flow chemistry: increasing the applicability of PffBT4T for organic photovoltaics

“…[49][50][51] Dehydrogenative cross-coupling and other types of direct arylation protocols have recently received an increased attention as they eliminate the need for toxic intermediates. [52][53][54][55][56] The direct arylation protocol allows the preparation of monomer 1a in 60% yield and employs two reaction steps less than the commonly used Stille cross-coupling approach. 3 This significantly simplifies the 'synthetic complexity' for the preparation of the monomers, classifying PffBT4T-2OD and derivatives, combined with their high efficiency, as potentially industrially viable candidates for solar cell applications.…”

Synthesis and Evaluation of Scalable D-A-D π-Extended Oligomers as p-Type Organic Materials for Bulk-Heterojunction Solar Cells

“…Despite their enormous potential, large scale applications of π-extended organic materials are hampered by the excessive cost of production, which does not yet take into account established sustainability indexes like the E factor (kg of organic waste/kg of product) [19]. E factor values for organic semiconductors are often in the excess of 10 4 , in some cases largely surpassing those for organic small molecules, which are active components of pharmaceutical formulations [20][21][22]. Our group has recently introduced a one-pot cascade methodology, comprising direct arylation (DHA) [23][24][25][26][27] and cross aldol condensations as the sequence of two alkalinemediated reactions in a single process.…”