Minimizing Recombination at the Perovskite/C₆₀ Interface through a Volatile Highly Dense Molecular Interlayer

Advancing inverted perovskite solar cells requires effective strategies to mitigate nonradiative recombination at the perovskite/C₆₀ interface. Here, we report a volatile material that forms a thin, dense interlayer that essentially eliminates the C₆₀-induced nonradiative interfacial recombination loss despite not directly passivating the perovskite surface. Ultraviolet photoelectron spectroscopy highlights that the molecule forms a positive dipole layer on the surface that aligns the perovskite and C₆₀ energy levels for electron conduction. Furthermore, the molecule’s volatile nature allows the use of a high-concentration solution that enables a high surface coverage (likely >99%) without increasing the thickness. The combination of these two effects yields an effective approach to suppressing interface recombination. The resulting triple cation perovskite solar cells achieved a power conversion efficiency of >25% and the devices maintain >90% of their initial efficiency after 1200 h of operation. Furthermore, the molecule is broadly applicable to various perovskite compositions and bandgaps.