Function Nickel Oxide for Perovskite LEDs: Energy Level Modulation and Hole Injection Optimization

Abstract Optimizing the architecture of perovskite light‐emitting diodes (PeLEDs), such as incorporating inorganic hole transporting layers (HTLs), is crucial for enhancing their operational stability. Nickel oxide (NiO x ) offers a unique combination of intrinsic stability, good electron‐blocking properties, excellent solution processability, and tunable optoelectronic properties, making it an ideal inorganic HTL. Understanding the basic properties of NiO x , and customizing its energy level help address the limitations in hole injection, enabling more efficient and stable display devices. This review begins with an overview of the band structure and surface chemistry of NiO x , focusing on the structure‐activity relationship between NiO x and its semiconductor properties. In the following section, the synthetic chemistry of solution‐process NiO x is addressed. The emphasis is placed on the possible correlation between the morphology of NiO x and its energy level. Next, strategies for tuning the energy level of NiO x are summarized. Finally, a brief prospect on NiO x ‐based PeLEDs is provided. It is hoped this review provides a new viewpoint for more stable and efficient PeLEDs.