High Luminance and Stability of Perovskite Quantum Dot Light-Emitting Diodes via ZnBr2 Passivation and an Ultrathin Al2O3 Barrier with Improved Carrier Balance and Ion Diffusive Inhibition

Carrier balance and ion diffusive inhibition are crucial to the external quantum efficiency (EQE) and stability of perovskite quantum dot light-emitting diodes (PQLEDs). Herein, an inorganic ZnBr2 ligand is used to passivate the Br vacancy on the surface of the perovskite quantum dots and, thus, near-unity photoluminescence quantum yield is achieved. With respect to energy alignment and carrier balance, poly[bis(4-phenyl) (4-butylphenyl) amine] (poly-TPD) is chosen to match with 1,3,5-tris (1-phenyl-1H-benzimidazol-2-yl) benzene (TPBi), and the fabricated PQLEDs exhibit the maximum luminance as high as 92,279 cd m(-2). In addition, an ultrathin Al2O3 layer is introduced between indium tin oxide (ITO) and poly(ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS) via atomic layer deposition (ALD). The Al2O3 buffer layer can precisely control the hole transmission rate, balance the carrier injection, and realize the improvement of EQE from 2.86 to 4.81%. The T-50 lifetime of the device is extended by about 30 times due to suppression of metal ion diffusion from ITO to the emission layer. Our work demonstrates the promising fabrication of highly efficient and stable PQLEDs via ALD interface engineering.