Direct (Hetero)arylation: A Tool for Low-Cost and Eco-Friendly Organic Photovoltaics

Abstract

Organic photovoltaics have attracted much attention in the past few years, mainly due to their ability to be fully printed at low cost and large scale. However, the organic semiconductors utilized as the active layer are typically synthesized using Migita−Stille or Suzuki−Miyaura cross-coupling, which is not cost efficient and may bring toxicity concerns. In the search for atom-economical synthesis, direct (hetero)arylation polymerization (DHAP) enables the activation of aromatic C−H bonds, both reducing synthetic steps of monomers and toxic reaction byproducts. In this issue, we will discuss the recent contributions on direct (hetero)arylation synthesis toward mass production of photovoltaic materials. The impact of DHAP on material efficiency will be addressed and compared to conventional coupling methods. The ongoing improvements will be discussed, as DHAP becomes more sustainable at higher scale and materials are observed as having higher quality.

Tuning the molar mass of P3HT via direct arylation polycondensation yields optimal interaction and high efficiency in nonfullerene organic solar cells

“…Reductive elimination of the cross-coupled product regenerates palladium(0) and generate cross-coupling thiophenes. This method has the advantages of synthetic feasibility (via a single step) 25,26 and high atom-economy (only breaks C-H/C-Br bonds). Moreover, the synthetic cost of P3HT via DArP is estimated to be less than 10 $ g À1 , based on a recent report.…”

Advances in applying C–H functionalization and naturally sourced building blocks in organic semiconductor synthesis

“…Direct arylation and oxidative C-H/C-H coupling are the two C-H activation involved synthetic routes for OSMs as green alternatives to the conventional synthetic methods, such as Suzuki and Stille couplings, due to their high atom economy (Scheme 2). [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] For instance, the atom economy of a Suzuki coupling shown in Scheme 1a is calculated to be 60%. If direct arylation and oxidative C-H/C-H coupling were used instead to synthesize the same organic semiconducting product in Scheme 1a, respectively, then the values of atom economy would be 80% for direct arylation and 99% for oxidative C-H/C-H coupling.…”

“…DArP, as an emerging subject in the field of OSM synthesis, has been reviewed many times in the past few years. [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] The semiconducting polymers synthesized via DArP are mostly linear homopolymers and alternating copolymers. When homopolymers are prepared using DArP, the monomer has a C-X (X = Cl, Br, I) bond and a C-H bond to proceed a head-to-tail polycondensation (Scheme 4, top).…”

“…Many scientific endeavors have been made to improve the environmental impact of OSMs, including shortening the synthetic routes by adopting C-H functionalization, applying green solvents, replacing the toxic and scarce metal catalysts with earth abundant (first row) transition metal catalysts, reducing the energy consumption by performing the synthesis under ambient conditions, as well as utilizing naturally sourced building blocks. [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] This review highlights the progress on enhancing the environmental friendliness of synthetic protocols, consisting of synthetic routes, reagents, reaction conditions, and building blocks of OSMs, made in the past four years to facilitate the large-scale production and commercialization of OSMs. Specifically, the purification and processing of OSMs are outside the scope of this review.…”

Impact of open‐shell loading on mass transport and doping in conjugated radical polymers

“…DArP is an environmentally benign and cost-effective polymerization method for synthesizing conjugated polymers. [35][36][37][38][39][40][41][42] Many polythiophene derivatives have been synthesized using DArP, including some polymers based on 3,4-alkylenedioxythiophenes (XDOTs). 40,[43][44][45][46][47][48][49] Relative to polythiophenes, XDOT-based polymers have distinct advantages in terms of their low oxidation potentials, high redox stability, and impressive charge capacity values.…”