Self-assembled molecular structure modification enables a high-performance hole-injection layer in perovskite light-emitting diodes

In perovskite light-emitting diodes (PeLEDs), a rational device architecture design is fundamental to the fabrication of high-performance devices. Recently, Self-assembled monolayers (SAMs) have been utilized in PeLEDs to enhance device performance due to their ability to modulate energy level alignment and their spontaneous formation into dense films. However, during the solution processing, SAMs because of their self-assembly properties, tend to form micelles, which can compromise the integrity of formed SAM. In this study, it has been observed that the introduction of methyl groups into the molecular structure of phosphonic acid-based carbazole SAMs helps to disrupt micelle formation, thereby leading to the creation of dense SAM. The use of SAM also strengthens the robustness of the poly(9-vinylcarbazole) layer, subsequently reducing the defect density in the perovskite layer and suppressing the process of non-radiative recombination. Consequently, PeLED devices developed with SAMs have demonstrated improved performance. These discoveries make a contribution to the development of new SAM materials for use in PeLEDs.