Metal halide perovskites have recently ascended as leading solution-processed semiconductor materials for optoelectronic applications.Rapid advances in the understanding of materials properties and the development of device architectures led to highly luminescent perovskite light-emitting diodes (PeLEDs) [1].PeLEDs consist of a pseudo-cubic crystal scaffold with a general chemical formula ABX3, in which A is an inorganic or organic cation (e.g., Cs+, CH3NH3+ (MA), or (NH2)2CH+ (FA)), B is the divalent metal cation center such as Pb2+ and Sn2+, and X is the halide anion (e.g.,Cl-, Br , or I).PeLEDs have achieved good performance with tunable emission wavelength across the entire visible spectrum and the near infrared region, but this has not been matched by the development of long-term device stability [2].The poor stability of PeLEDs can be attributed to the imperfect device design (e.g.,imbalanced charge injection) and the materials instability, which relates to its low crystal formation energy and the ionic nature of the perovskite emissive layer.The low crystal formation energy underlies the decomposition of perovskite under device operating conditions, which is further accelerated by heating, humidity, and light, and thus impairs the luminescence properties of the emission layer.The ionic nature of perovskite, on the other hand, makes the surface atom-ligand bonds susceptible to detachment/reattachment.The ligand-free, unprotected surface atoms are prone to interact with water and oxygen, introducing surface traps that promote non-radiative recombination of charge carriers and impair the electroluminescence (EL) efficiency.