Efficient and Stable Pure Green All-Inorganic Perovskite CsPbBr₃ Light-Emitting Diodes with a Solution-Processed NiOx Interlayer

The perovskite-based optoelectronic applications always suffer from stability issues, due to the intrinsic chemical instability of the perovskite materials. Besides, poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) is always utilized as an anode buffer layer in thin-film perovskite light-emitting diodes (PeLEDs), which may lead to stability issues due to the hygroscopic and acidic nature of PEDOT:PSS. In this paper, inorganic metal oxide NiO x is employed as a hole injection layer (HIL) and hole transport layer (HTL) to substitute detrimental PEDOT:PSS in all-inorganic PeLEDs. Then fully covered CsPbBr 3 polycrystalline films are fabricated by using a one-step spin-coating method based on nonstoichiometric and polymer-assisted perovskite precursor solutions. The optimized films not only have compact morphology but also have excellent photoluminescence quantum yield (PLQY). Encouragingly, by introducing a metal oxide NiO x, the CsPbBr 3 PeLEDs show a maximum luminance of 23 828 cd m –2 and maximum current efficiency (CE) of 9.54 cd A –1, which lead to a 1.6-fold and 3.3-fold increase compared to the PeLEDs with a PEDOT:PSS HIL. Besides, the inorganic PeLEDs show high color purity with a full-width at half-maximum (fwhm) of only 16 nm. The combination of inorganic NiO x with inorganic perovskite also shows improved operation stability of devices, which paves the way for highly efficient all-inorganic PeLEDs.