Microwave-Assisted Classic Ullmann C–C Coupling Polymerization for Acceptor-Acceptor Homopolymers

Abstract

Developing cheap, clean and atomic-efficient synthetic methodologies for conjugated polymers are always critical for the field of organic electronics. Herein, classic Ullmann coupling polymerization is developed to synthesize a series of Acceptor-Acceptor (A-A) type homopolymers with microwave-assistance, which are supported by nuclear magnetic resonance (NMR), matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF), elemental analysis (EA) and gel permeation chromatography (GPC). The physicochemical properties of these polymers are studied by UV-vis spectroscopy, cyclic voltammetry (CV), thermal gravimetric analysis (TGA), and density functional theory (DFT) calculation. Furthermore, these A-A homopolymers are used as acceptors for all-polymer solar cells (All-PSCs), affording a promising efficiency of 3.08%, which is the highest value for A-A-homopolymer-based organic solar cells.

N–B ← N Bridged Bithiophene: A Building Block with Reduced Band Gap to Design n-Type Conjugated Polymers

“…This is due to the highly delocalized LUMO over the whole polymer backbone of the two polymers , (Figure S10). Noteworthy, the LUMO level of BN-X1 is among the lowest for conjugated homopolymers reported so far. ,− The UV–vis absorption spectra of BN-X1 and BN-X2 in chlorobenzene solution are presented in Figure b. BN-X1 and BN-X2 show absorption peaks at 657 nm and 691 nm, respectively.…”

Acceptor–acceptor-type conjugated polymer semiconductors

“…In addition, the Ullmann reaction (Scheme 2) was first used by Huang's group [77] to synthesize A-A-type homopolymer based on NDI and PDI in 2019. The classic Ullmann coupling reaction has obvious advantages on the cheap and non-toxic Cu catalyst and simple operation [78,79].…”

“…Despite the low-lying LUMO level, good electron transport and broad absorption, PDI polymers were greatly delayed because of the large steric hindrance between monomers to inhibit the efficient charge transport between polymer chains [126][127][128]. For instance, Huang's group [77] synthesized a PDI homopolymer (f4) to separately match it with two donors (PTB7-Th and PBDB-T) to investigate the photovoltaic performance. The maximum PCE of PSCs based on PTB7-Th:f4 was 3.09%.…”