Hetero Bis-Addition of Spiro-Acetalized or Cyclohexanone Ring to 58π Fullerene Impacts Solubility and Mobility Balance in Polymer Solar Cells

Designing Alternative Non-Fullerene Molecular Electron Acceptors for Solution-Processable Organic Photovoltaics

Until recently, solution-processable organic photovoltaics (OPVs) mainly relied on fullerene derivatives as the n-type material, paired with a p-type conjugated polymer. However, fullerene derivatives have disadvantages that limit OPV performance, thus fueling research of non-fullerene acceptors (NFAs). Initially, NFAs showed poor performance due to difficulties in obtaining favorable blend morphologies. One example is our work with 2,6-dialkylamino core-substituted naphthalene diimides. Researchers then learned to control blend morphology by NFA molecular design. To limit miscibility with polymer while preventing excessive self-aggregation, non-planar, twisted or 3D structures were reported. An example of a 3D structure is our work with homoleptic zinc(II) complexes of azadipyrromethene. The most recent design is a planar A-D-A conjugated system where the D unit is rigid and has orthogonal side chains to control aggregation. These have propelled power conversion efficiencies (PCEs) to ∼14 %, surpassing fullerene-based OPVs. These exciting new developments prompt further investigations of NFAs and provide a bright future for OPVs.

Comment on "Fullerene-based materials for solar cell applications: design of novel acceptors for efficient polymer solar cells--a DFT study" by A. Mohajeri and A. Omidvar, Phys. Chem. Chem. Phys., 2015, 17, 22367

Though a linear correlation has been recently reported between mean polarizabilities of the fullerene derivatives and open-circuit voltages of organic solar cells based on them, we demonstrate that there is no general dependence between these two values and some related quantities (anisotropy of polarizability and LUMO levels).

Regioselective addition of Grignard reagents to tosylazafulleroid and derivatization to 1,2-disubstituted [60]fullerene

Grignard reaction with tosylazafulleroid selectively gave tosyl aminylfullerene with the relatively rare 1,2-configuration, via [5,6] ring-closure and CN-bond scission.