Isoindigo has recently attracted considerable interest as an electron-deficient building block for conjugated polymers. Polymers based on isoindigo have demonstrated high performances in polymer solar cells (PSC) and in organic field-effect transistor (OFET) devices. The success of isoindigo as a building block results from the combination of several important characteristics such as low-lying frontier orbital energy levels, backbone planarity and extended conjugation, a large local dipole, good solubility after N-alkylation and ease of synthesis in large scale. This mini-review highlights the recent advances in the synthesis of isoindigo related polymers and their applications in PSC and OFET devices.

N -acylated polymers displayed significantly reduced LUMO levels and improved reversibility of reductive doping compared with their N -alkylated counterparts.

Design and synthesis of novel monomers may create new opportunities for high performance semiconducting polymers. The synthetic modification of an isoindigo related building block based on rational design has been carried out in this study. An expanded isoindigo unit (IBTI) with 5,5′-divinyl-2,2′-bithiophene as a conjugated bridge has been successfully incorporated into a donor–acceptor conjugated polymer, PBDT–IBTI. The new polymer showed broad absorption and a large extinction coefficient in the visible region. The optical bandgap, HOMO and LUMO levels of this new polymer are 1.71 eV, −5.24 eV and −3.72 eV, respectively. The polymer solar cells based on PBDT–IBTI and (6,6)-phenyl-C61 butyric acid methyl ester (PC₆₁BM) blends achieved a PCE of 6.41%. This work has demonstrated that IBTI is a promising building block for organic photovoltaic (OPV) polymers. These findings have also revealed the versatility of oxindole as the basic building element for isoindigo-like conjugated monomers.

1,8-Naphthoylene(trifluoromethylbenzimidazole)-4,5-dicarboxylic acid imide (NTFBII) derivatives were synthesized. The OFET devices based on these new materials showed typical n-type OFET behavior and achieved an electron mobility as high as 0.10 cm² V⁻¹ s⁻¹ with good bias stress stability.

A novel, star‐shaped electron acceptor, DMTPA‐PDI₃, derived from a planar dimethylmethylene‐bridged triphenylamine core with three acetylene‐linked perylene diimide (PDI) units is developed as a nonfullerene acceptor for organic solar cells (OSCs). DMTPA‐PDI₃ manifests significantly reduced intramolecular twisting, enabling sufficient system‐wide π‐electron delocalization leading to broadened spectral absorption and raised lowest unoccupied molecular orbital level. As a result, higher and more balanced hole and electron transport properties are observed. Active layers for OSCs comprising DMTPA‐PDI₃ acceptor and PBT7‐Th donor exhibit suppressed intermolecular aggregation, giving rise to uniform nanophase network formation. These OSC devices have afforded respectably high power‐conversion efficiency of about 5%.