Tunable Anode Work-Function by Self-Assembled Monolayers for High-Performance Pure Blue Light-Emitting Diodes Low Driving Voltage

Organometallic trihalide perovskites have garnered significant attention for their potential in light-emitting diode applications, thanks to their unique characteristics including excellent color purity, color tunability, and ease of solution processing through scalable printing technology. Presently, perovskite emitters have achieved comparable electroluminescence and quantum efficiency to organic and quantum-dot display technologies in green and red-emitting perovskite light-emitting diodes (PeLEDs). However, blue-emitting PeLEDs still face challenges in terms of electroluminance, operational stability, and efficiency, primarily due to the relatively wide bandgap of the perovskite emitters (<i>E</i>_g &gt; 2.5 eV), which thus requires high driving bias for device operation. In this study, we propose a straightforward interfacial engineering approach to reduce the driving voltage of pure-blue PeLEDs by employing self-assembled monolayer (SAM) molecules on the indium tin oxide (ITO) electrode. The SAM layer facilitates the control of the electronic structure of the ITO surface by modulating its work function, thereby improving hole extraction properties at the lower internal interface. Furthermore, the functionalized SAM molecules interact with the under-coordinated perovskite lattices, providing interfacial interaction with the perovskite layers and facilitating radiative carrier recombination at lower driving bias. These desirable characteristics of SAM molecules enable enhancements in the electroluminescence and quantum efficiency of pure blue emission while requiring lower driving voltage. Moreover, the superior properties of the perovskite film, coupled with the reduced driving voltage, contribute to an extended operational stability of blue electroluminescence in PeLEDs. Consequently, this strategy demonstrates the remarkable potential of achieving high-performance PeLEDs with blue light emission, which is highly attractive for full-color perovskite display technologies.