Organic Hole‐Transport Layers: An Innovative Approach for Efficient Perovskite Light‐Emitting Diodes

Organic–inorganic‐halide‐perovskite (OIHP) based light‐emitting diodes (LEDs) are becoming more and more well‐described as having multiple potential uses in lighting and display technology, owing to their broad color gamut and high color purity. Recent research reveals that hole‐transport layers (HTLs) perform crucial roles in realizing high‐performance and highly stable perovskite light‐emitting diodes (PeLEDs). However, the exploration of organic HTLs for obtaining efficient PeLEDs has lagged behind compared to electron‐transport layers. In the past few years, some innovative HTLs have been developed for PeLEDs, which have demonstrated excellent performances in the devices. It has been established that HTL/OIHP interface has a significant impact on the crystallization behaviors and electrical properties of OIHP film. Herein, different types of organic HTLs (polymer/small molecule) used for PeLEDs are discussed. Also, the mechanism of action of those HTLs in perovskite devices is also presented. Moreover, the recent progress of organic HTLs in blue, green, and red PeLED devices is highlighted. Furthermore, the strategies to improve the performance of existing standard HTLs are also reviewed. Additionally, the challenges present in the PeLED technology are briefly summarized. Lastly, viewpoints regarding the ongoing obstacles and forthcoming prospects are emphasized. Interfacial engineering is pivotal to realizing a balanced charge injection and to developing high‐quality defect‐free perovskite crystals with uniform morphology. In this regard, organic hole‐transport layers have evolved as promising anode interface modifiers for the construction of highly efficient perovskite light‐emitting devices.