Unlocking performance: the progress and analysis of hole-injection materials (HIMs) in advancing organic optoelectronics

An essential prerequisite for the efficient functioning of semiconductor devices is the optimal charge transfer between electrodes and organic active regions. With the design of molecules and the upgrading of devices, there has been rapid development in hole-injection materials (HIMs) and their applications, which offer distinct advantages such as higher hole-injection efficiency, better interface stability, and broader process compatibility. However, they face several scientific challenges. The interface may still suffer from Schottky barriers due to slight energy-level mismatches or surface roughness, negatively impacting the device efficiency. Additionally, the corrosive effects of the processing solvent at the material interface can affect the device lifespan. More importantly, the challenges in achieving proper energy-level alignment and the trade-off between molecular hole mobility and device structure must be addressed. This review primarily discusses different types of hole-injection materials used in various organic optoelectronic devices, summarizes their latest developments and applications, and discusses the challenges and issues that need to be overcome in the future development of this field.