Review of molecular engineering for horizontal molecular orientation in organic light-emitting devices

Abstract

Organic light-emitting devices (OLEDs) are widely used in next-generation eco-friendly solid-state display and lighting technologies. Most key optoelectronic functions of organic films used in organic semiconductor devices are dependent on two important factors: the electronic properties of single molecules, and the molecular orientations. The molecular orientation has recently attracted considerable attention, and been recognized as a crucial parameter for determining key optoelectronic functions of organic devices, such as device lifetime, efficiency, ionization potential, and carrier mobility of semiconductor amorphous films. In this review, we discuss horizontal molecular orientation from a molecular engineering perspective considering the three essential layers of OLEDs: the hole transport layer, electron transport layer, and emissive layer. In addition, we address the future challenges of next-generation OLED materials.