Laser Manufactured Nano-MXenes with Tailored Halogen Terminations Enable Interfacial Ionic Stabilization of High Performance Perovskite Solar Cells

Formamidinium (FA)-based perovskite promises high power conversion efficiency in photovoltaics while it faces awkward spontaneous yellow phase transition even at ambient conditions. This has spurred intensive efforts which leave a formidable challenge on robust anchoring of the soft perovskite lattice. Present work pioneers the rational design of interfacial ionic-bonding between halogen-terminated nano-MXenes and perovskite for effective retarding of the lattice instability in FA-based perovskites. The robust heterointerface between perovskite and nano-MXenes results also in effectively modulating the deep-energy-level defects, lowering the interfacial charge transfer barrier, and tuning the work function of perovskite films. Benefiting from these merits, unencapsulated FA-based perovskite solar cells after the ionic stabilization (champion efficiency up to 24.17%), maintain over 90% of their initial efficiency after operation at maximum power point under continuous illumination for 1000 h, and retain more than 85% of their initial efficiency even after annealing for 1000 h at 85 °C in inert atmosphere.