Crystalline organic thin films for crystalline OLEDs (III): weak epitaxy growth of phenanthroimidazole derivatives with a dual inducing layer

Abstract

Crystalline organic thin films based on phenanthroimidazole derivatives, particularly 2FPPICz, exhibit significant potential for application in high-performance organic light-emitting diodes (OLEDs) due to their ordered molecular structure and superior optoelectronic properties. This study proposes a novel dual inducing layer structure that simultaneously achieves energy-level alignment, enhanced charge injection, and high-quality crystalline film growth. Specifically, a BP2T inducing layer is introduced between the anode and conventional BP1T layer to enhance hole injection while maintaining high-quality epitaxial growth. The BP2T layer effectively bridges the energy-level mismatch at the anode interface and reduces lattice mismatch between BP1T and 2FPPICz, facilitating the formation of large-area, continuous crystalline films. Comprehensive characterization using atomic force microscopy (AFM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) confirms the improved structural coherence and epitaxial relationships within the dual inducing layers. The hole-only device demonstrates a 136% increase in current density at 1 V, highlighting the enhanced charge injection efficiency. These findings provide a strategic approach for optimizing crystalline OLED performance through a tailored dual inducing layer structure, paving the way for advanced optoelectronic applications.