Improving the Stability of Organic–Inorganic Hybrid Perovskite Light-Emitting Diodes Using Doped Electron Transport Materials

Herein, organic–inorganic hybrid perovskite light-emitting diodes (PeLEDs) are fabricated under ambient air and all-solution conditions. A novel N₂ gas blowing step is applied during spin-coating of the precursor solution to obtain uniform methylammonium lead bromide (MAPbBr₃) perovskite nanocrystal films with fewer surface and interfacial defects than solution-processed perovskite films. Furthermore, polyethylenimine (PEI) and poly[9,9-dioctyl-9′,9′-bis[3-(trimethylammonio)propyl][2,2′-bi-9H-fluorene]-7,7′-diyl] (PFN) are used as doping agents in the widely used electron transport layer (ETL) material, 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi), and act as passivation agents between the rough surface of the perovskite film and the ETL. Consequently, the high surface work function of PEI- and PFN-doped TPBi results in reduced and balanced injection of electrons in the perovskite light-emission layer (EML) of the PeLEDs, producing a maximum luminance (L) up to 14 358 and 11 465 cd m⁻² for the PEI- and PFN-based PeLEDs, respectively. The doped-ETL-based PeLEDs also show a 3.6 times longer L₅₀ (i.e., the time needed for a 50% reduction in the initial value of L operated at 4 V) than the pure TPBi-based PeLEDs, which need a separate poly(methyl methacrylate) (PMMA) film to act as the passivation layer between the EML and ETL.