The surface of indium tin oxide (ITO) was modified with bolaamphiphilic (BA) materials to tune the energy-level alignment of electrodes in optoelectronic devices (OEDs). Tuning the energy-level alignment of the electrode is crucial for enhancing OED efficiency by improving carrier injection. Although the dielectric properties of organic solvents influence the formation of BA self-assembled monolayers (SAMs), our study found that the intermolecular forces of the dissolved BA materials and the solution medium are more important for the formation of a well-ordered film on the electrode. Our results also showed efficient tunneling phenomenon between the electrode and the hole transport layer (HTL) using BA material. The holes were transported to the tunnel junctions where the Fermi energy was sufficiently close to the HOMO band of the BA. Therefore, the tunnel barrier height of the ITO/HTL of the OED was reduced, and favorable conditions for hole injection was created, resulting in a 2-3 times increase in luminance and current density. It is believed that the larger area of interface contact between electrode/BA/HTL and the formation of wellordered BA layers are responsible for the improved performance of the BA-modified electrode surface and OED.

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This study investigated the electro-optic properties of organic light-emitting diode (OLED) devices with the addition of an interlayer. A device with the perfluorododecyl-1H,1H,2H,2H-triethoxysilane–perfluorotetradecyl 1H,1H,2H,2H-triethoxysilane mixture (hybrid solution) membrane applied to the hole injection layer (HIL) using a self-assembled monolayer (SAM), along with N,N’-Bis (naphtha-len-1-yl)-N,N’-bis(phenyl)-2,2’-dimethylbenzidine (α-NPD) applied to the hole transport layer (HTL), was fabricated and subsequently assessed. Compared to the device without an HIL, the device with HIL using SAM showed a luminance of 1630.16 (Cd/m2) at the maximum cut-off voltage of 11 V, and the efficiency was increased to ≥200% from the initial turn-on voltage of 3 V to the maximum cut-off voltage. These results suggest that adding an interlayer and the consequent carrier ladder effect led to more efficient injection and transport, possibly lowering the hole injection barrier and allowing excellent power efficiency.

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