Overcoming C60-Induced Nonradiative Recombination via Interfacial Embedding of BiOBr Flakes in Inverted Perovskite Solar Cells

The presence of C60-induced nonradiative recombination tends to deteriorate the overall efficiency of inverted perovskite solar cells (PSCs). To alleviate this problem, ultrathin BiOBr flakes possessing a unique self-induced internal electric field (SIEF) are embedded at the interface between perovskite and C60. SIEF, originating from the nonuniform charge distribution within the BiOBr lattice, tends to be perpendicular to the heterointerface of perovskite/C60 because of the designed special (001) facet. This precise arrangement facilitates electron extraction and hole blocking, yielding a field-effect mediated passivation. Also, the desired surface atomic structure on the BiOBr(001) facet can chemically passivate the perovskite surface defects via the formation of a Pb–O bond. Combining these dual passivation effects with favorable band bending, the application of BiOBr boosts the efficiency of inverted PSCs up to 24.36% with a substantially improved long-term stability. This work demonstrates an effective way to overcome efficiency and stability limits of inverted PSCs.