Organic-inorganic hybrid perovskite materials demonstrate promising applications in high-efficiency perovskite solar cells (PSCs) with a certified power conversion efficiency (PCE) of 25.5％ (https://www.nrel.gov/pv/cell-efficiency.html).However, intrinsically volatile and thermally unstable nature of the organic cations result in poor thermal stability of organic-inorganic hybrid perovskite materials, hampering the commercialization of organic-inorganic hybrid PSCs[1].All-inorganic CsPbl3-xBrx (x =0-3) perovskites have been attracting great attention in recent years because of their higher thermal stability[2].Among the reported CsPbl3-xBrx perovskites, CsPbl2Br bears a reasonable balance between bandgap and phase stability, thus becomes the most extensively studied material[3-15].Though there are many works aiming at achieving high-efficiency CsPbl2Br PSCs, improving the photostability of CsPbl2Br PSCs is another key for commercialization of all-inorganic PSCs.Intriguingly, it has been reported that CsPbl2Br is susceptible to make light-induced phase segregation, i.e.severe segregation of CsPbl2Br to low-bandgap I-rich and wide-bandgap Br-rich domains via ion diffusion, leading to obvious current-voltage hysteresis and decrease of stabilized power output (SPO)[16-20].Such a light-induced phase segregation can be suppressed by optimizing the interface between perovskite layer and charge-transport layer[18, 19].