Efficient Blade-Coated Wide-Bandgap Perovskite Solar Cells via Interface Engineering.

Most high-efficiency all-perovskite tandem solar cells use a "superstrate" configuration, integrating a wide-bandgap (WBG) top subcell and a narrow bandgap (NBG) bottom subcell. However, this structure suffers oxidative degradation due to easily air-exposable bottom NBG subcells. A "substrate" structure offers improved stability for tandems by encapsulating the NBG top subcell with the air-stable WBG bottom subcell. However, conventional WBG perovskite solar cells (PSCs) using water-based NiOx interlayers hinder their fabrication on top of the NBG subcells in an inert atmosphere. To overcome this, we developed a nonaqueous NiOx nanoparticle dispersion, enabling interlayer fabrication inside a glove box. The blade-coated NiOx interlayer facilitated the formation of a densely packed 2PACz (2-(9H-carbazol-9-yl)ethyl]phosphonic acid) monolayer hole transporting layer (HTL). The energetically aligned 2PACz molecules reduced minority carrier recombination at the NiOx/perovskite interface. As a result, the fully scalable 1.77 eV WBG PSCs employing a NiOx/2PACz hybrid HTL delivered a champion power conversion efficiency of 17.4%.