Bifacial passivation towards efficient FAPbBr₃-based inverted perovskite light-emitting diodes

A unique technique to passivate both bottom and top sides of perovskite has been successfully developed to achieve highly efficient inverted perovskite light-emitting diodes (PeLEDs). For the bottom passivation, an organic/inorganic hybrid electron transporting layer (ETL) replaces the widely adopted inorganic ETL to overcome the disadvantages of the pure inorganic ETL. The ZPM (ZnO-in-polymer matrix) ETL, which consists of ZnO nanoparticles blended into polyvinylpyrrolidone, not only passivates the surface defects of ZnO nanoparticles, but also improves the morphology and stability of FAPbBr₃ film. For the top passivation, smaller grains and a FAPbBr₃/PEA₂PbBr₄ 3D/2D hybrid structure are obtained by applying a small amount of PEABr solution. The synergetic interplay of organic/inorganic hybrid ETL and organic halide salt surface modification substantially shrinks the grain size to facilitate radiative recombination, and suppresses non-radiative recombination both at the interface of ETL/perovskite and HTL/perovskite, and in the perovskite layer. As a result, the highly efficient green PeLED sets a new record of device performance for FAPbBr₃-based inverted PeLEDs, with current efficiency of 39.7 cd A^-1, external quantum efficiency of 9.0%, power efficiency of 46.4 lm W^-1, maximum luminance of 6.03 × 10⁴ cd m^-2, and half-lifetime of 297 minutes at an initial brightness of ∼100 cd m^-2.