Surface Passivation of Lead Halide Perovskite Solar Cells by a Bifacial Donor-π-Donor Molecule.

Surface passivation is key to the power conversion efficiency (PCE) of organic-inorganic lead halide perovskite solar cells (PSCs). Herein, we report a novel molecular concept of a -symmetric -type bifacial donor-π-donor (D-π-D) passivation molecule (a racemic mixture of enantiomers) with hydrophobic phenyls and hydrophilic tetraethylene glycol-substituted phenyls on each face of the indeno-[1,2-]fluorene π-core. In addition to this bifacial amphiphilic π-core unit, triphenylamine, a well-established passivation donor, effectively passivated the PSC surface, facilitated hole transfer, and increased the maximum PCE from 18.